EXTREMELY TERRIBLE SERVICE

i receive a call from Mtn sometime in November selling me a contract sim card and was later told that i don't qualify, but mid December i got call from the Courier with my "parcel" which i told them to return to the supplier as i made other arrangements and i was told to call Mtn to cancel .i have being trying to call Mtn to cancel this as i have not received the sim card as yet i am not winning with them. As if that was not enough they debited my account and my old sim card is now not working i cannot make calls, load airtime/data. They are not helpful at all.