I want to cancel my mobile subscription from abroad

I have called KPN from abroad on multiple occasions (waited up to 40+ min) but they aren’t picking up the phone, I wrote a letter to cancel my contract but nothing still, I am abroad from july 2022 and I won’t pay extra 320€ fines because of horrible customer service, I will only pay existing fees for September and that’s it. I couldn’t pay earlier anyway cause I didn’t have the money, sim card wasn’t used since late july 2022