Terrible service

I cancelled a contract with MTN after it came to expiry. MTN still bills me and i called them numerous times they don’t want to assist me. The call center people just drop the call after I tell them about my problem. They just say we are transferring you. To make matters worse MTN sent a negative report about me to the credit bureau which is affecting me negatively yet I have literally done nothing wrong. I still can’t get help to today.