@dusankovacevic Welcome! This could an interesting one. So… before I say anything, could you please update your profile with your zip code, house number, the ‘new -not wanted- phone number’ and your ‘lost’ phone number. The information in your profile is only visible for KPN Moderators, so it doesn't matter where you enter these details. 
I'll try my best to port the number retroactively! 

Hi @Lisa , I have sent you a private message with all the details.

Please let me know if you need anything else from my side.

Thanks!

@dusankovacevic Thank you for all the details behind this issue. So, it is a bit more complex than I thought/hoped it would be. I asked our back-office to solve this problem. They have access to our mobile network. Regarding your phone number, there is hope since we save/reserve a used number for approximately 1 year before it is available for someone else. I'll come back to you when I received a response from them. I gave them permission to fix it (when possible) immediately. So, if it is solvable you will notice this immediately. 

Hello @Lisa , have you received any update regarding my issue?

Thanks,

Dusan

@dusankovacevic Ahh, so you didn't receive any response yet. I handed this case to a different department. I'll e-mail them for an update! 

@dusankovacevic The problem is solved.  Could you please check this for me? 

@Lisa thanks a lot for the help!!!

everything is working now!

Good to hear!! wish you a good weekend already.