Incapacity of fixing billing issue for more than 6 months

I informed them of an incorrect billing on my account. I was credited for the incorrect amount, but the additional contract was not removed as promise. After Endless emails with no response, I informed them to cancel my contract with them, no surprise, also no one responded to that instruction. Now, they send me a notice i'll be handed over for none payment. I tried phoning them, surprise, surprise, no one bothers to answer the phones as well.