Hi @ChiaraM. and welcome to our forum. I can imagine the frustration when the contract isn't terminated yet. The department in charge of terminating the contracts is not active on this forum, however you could call them using +31 6 1200 1200. On business days they’re available between 8:00 - 20:00 and on Saturdays between 9:00 - 17:00 (Dutch timezone). They don't have an e-mail address, but if contact is easier for you digitally, you can also go to kpn.com/contact > wijzigen > opzeggen > mobiel > verhuizen/emigreren. Then scroll all the way down, and you'll find a chat option there looking like this: 

The department in charge of terminating contracts is available through chat as well, during the same opening hours. Hopefully you’ll get some clarity this time around, and the contract will be terminated soon! 

As I mentioned in the post above, I have already contacted that department several times - they mention they don’t know what’s happening, that they will talk to their colleagues and then call me back. They have never called back. As to the chat function, there are no operators available so it does not work and tells you to call the client service. I would really appreciate some actual help.

Well, seems a known bad practice / attitude by KPN.

This is not the first subject a user is abroad already for several months, sending in all details, time after time, and still paying and paying, not ending the contract by KPN. Every time different excuses by KPN, but no ending.  A real nightmare how KPN do act and abuse of power.

I do give you the advice to cancel / reverse bank payment immediately.
You can reverse payed amounts for three months by yourself by tele-banking.   Not longer.
(Hope you didn't wait that long).

But keep in mind eventually "last" extra calculated costs of phone calls or e.g. rented movies or so, that you have used maybe, during "official" time you was in The Netherlands, for paying.
(You can pay separately - as you can not differentiate / divide reverse bank payment amounts).
Did you send back the loan modem / TV-box to KPN??  -  So you have no overdue debts.

And should contact your bank office that you cancel / de-authorize the automatic payment by KPN.
If KPN still take money, you can file a complaint by the bank organisation itself.
So KPN shall be compromised by their attitude by the bank organisation.

Just send a printed copy of the needed papers ( proof of registration abroad ).
Plus write that you end the KPN account from your side, as KPN is not responding in a way that can be acceptable.  Including KPN account number, name etc. - and do send it once in an envelope
by registered mail - e.g. DHL or other post organisation (so you have a receipt of the sending).

And send it to:

KPN Klantenservice,  t.a.v. Opzeggen
Postbus 235
2400 AE  Alphen aan den Rijn  -  NL

               The Netherlands

By that you have fully complied with the legal termination of your contract.

If it's not working through the chat either then I'll approach one of my colleagues directly about this. Could you fill out your forumprofiel with your postal code, house number, and the name and date of birth of the subscriber? Please add the cellphone number you’re available on as well, if it's a Dutch cellphone number. If not, please add your e-mail adress under ‘persoonlijke opmerkingen’. If you give a signal here when you’ve done that I can look up your subscription and contact one of my colleagues about it! 

I just did. I don’t have a Dutch number as I don’t live in The Netherlands anymore; I have indicated my email and my OLD Dutch address associated with my subscription, where I am NOT registered any longer - as someone else is living there now. I’d appreciate if you could get back to me on this, thank you. 

Thank you! I've asked one of my colleagues whether he can help us with terminating your subscription. I hope I'll hear back from him soon, but I can't say when he's able to pick this up. Nevertheless I'll keep you posted and I'll let you know as soon as I've heard back. 

Hi @ChiaraM.! I received a reply. My colleague states that the following applies: 

“The original form needs to be supplied with a stamp and an autograph for it to be approved. Once that's been handed in the termination will be approved”

In your first message you say that you handed in the proof twice, did the second time contain the form with the stamp and the autograph? If so, where did you send this to? Then I can follow it up.

As I have now mentioned a hundred times to all the operators I’ve spoken and wrote to, as de-registration from The Netherlands now happens online (don’t know how this is not something you are aware of), I have received a confirmation of de-registration via email from the Municipality, which is the one I have sent as proof. I have spoken on the phone with the municipality and they told me that this is the one form that they send out, they are not sending anything else. The form is a pdf and does not have a stamp / autograph. I don’t know what to do about the situation any longer, I have asked your colleagues how to get this form that you are asking but received no reply. This is an insane situation, as I am moved out of the country for more than a month now and I am still dealing with this. As I cannot keep loosing my time and efforts for this impossible situation where no one is able to tell me what to do, I have now blocked all payments and if I don’t hear from anyone who can terminate my contract there’s nothing more I can do. 

Thanks for letting me know. I'm still working on the situation, so it's not settled yet. Don't despair! Can you find when you sent this and to which e-mail address? Then I can refer my colleague to that e-mail and add your reply here for context.

I used your online form and submitted it on June 21st. 

Thanks! I've let them know. I've also asked them if the proof you’ve sent isn't sufficient, what else they'd need exactly in order to get the subscription terminated. I'll keep you posted! 

And I've already received a reply. Unfortunately they keep mentioning the proof of deregistration with a stamp and an autograph, and state that the proof sent to them on the 12th of July was not approved because it did not contain these things. The following are accepted as proof: 

• Proof of deregistration from the municipality
• Your employment contract abroad
• A statement from your study institution abroad

You could e-mail them your proof of deregistration from the municipality againn, to opzeggen@kpn.com. Add to that that you cannot get a stamp or signature, because this is all the proof the municipality supplies. If possible, also add your employment contract abroad, or a statement from your study institution abroad. That should be more than sufficient for terminating the contract. 

You could also try contacting them directly to get clarification on why the proof of deregistration keeps getting rejected. From abroad you can contact them through +316 1200 1200. They’re available on business days between 8:00 - 20:00 and on Saturdays between 9:00 - 17:00 (Dutch time). I'm sorry I couldn't get this sorted for you, but I hope that these steps help you in getting the contract terminated. At least you'll have a way to contact them directly if necessary. 

@ChiaraM. 
Yes - nowadays - most is done by online services, without stamps.
Keep in mind what I wrote before (by this message), and you have done your thing.

Cancel / reverse bank payment immediately.
You can reverse payed amounts for three months by yourself by tele-banking.   Not longer.

As you already was intending to do as written here.

I have now blocked all payments and if I don’t hear from anyone who can terminate my contract there’s nothing more I can do.

Kudo's    That is the best thing to do, and don't take more time an energy in it.
Do reverse bank payment, by the day you went abroad.
(The day of de-registration via email from the Municipality).  No day longer!!

As it is a "Never ending story" by KPN.  Every time another excuse.
Let KPN cook in their own unreasonable terms to terminate subscriptions. 
While it is clear that you have emigrated, and KPN can not give services in another country.
It is not necessary to pay for internet services what can not be delivered abroad  - by law.

@Sanne_M 
This is going to be my last reply. 
I have already done all the things you mentioned (called, sent emails explaining my situation), with no result - that’s why I wrote in this forum in the first place. I am therefore not going to do them again. 
I do not have a statement from a study institution, as I am not a student, and I am not currently employed. But this does not matter, as I did move out of The Netherlands, with de-registration, nonetheless.
After weeks and weeks of contact, none of you have been able to tell me how to get this proof with stamp and signature that you keep bringing up. Therefore, this is out of my hands now. 

I have the same issue. KPN is charging me even after months moving abroad. I've sent proof from the municipality.
Then as this proof was denied multiple times (which per se is already ridiculous) I was advised to send a letter from my new employee abroad and my new address.

I've sent multiple times all the proofs and still receive charges. I denied to pay them all as I don't judge the right thing to do and it resulted in KPN placing me into "the list of clients that don't pay", which will make it a lot hard to hire anything if I move back to The Netherlands. LUCKYLY, I don't plan to move back to the NL never again.