After moving abroad and cancelling my contract I got charged 60.50 for data in IND

I had requested to close my sim/cancel my subscription and my number on August 5th by August as I was moving out of the country by end of August. I had notified the same to the customer service executive over call when I requested the cancellation.

I fail to understand why KPN chose to send me the invoice for my cancelled subscription on September 9th AFTER I had already left the country and no Dutch bank account to pay the invoice with. Don’t you think your customer service representative should be mentioning this crucial information over the call when asked to cancel a sim?
Also, despite me notifying well ahead of time that I am leaving the country and I wanted my sim turned off ASAP, why you would keep it functioning and then charge me for usage abroad erroneously even when the phone containing the sim was not even used during the end of August?

Also, how is it that it's nearly impossible to contact you guys outside of NL? Why is the default expectation that I would expend enormous amount of money towards international call charges to contact you over a phone call? Why is there no way to reach out to you by email? 

If you want your customers to close their invoices after leaving the country, then please provide an easy way for them to do so or resign to the fact that they would not settle it. I firstly see no option to pay my bill anymore as the subscription is closed and also see no way to pay it from overseas as I currently have no Dutch bank account.

Please reach out to me on my registered email so I can collect details on how to pay your invoice as you guys are clearly useless at providing information upfront.