Bad service from MTN

Mtn never even told me why i was handed over, they never made contact with me in 2 years time, when i go the store they cannot assist me, still want to know why i was handed over , because i did send them a cancellation email after my contract ended, when i called they told me they got technical problem and never received my email but when i gave them my the refence number they picked up my email and told me i must still pay its not they fault, out of the blue i received a email from CSS MY ACCOUNT HAS BEEN HANDED OVER, and i told the agent im not Going to pay until i get a invoice from MTN i requested a invoice still nothing