Ridiculoud

I have 2 contracts with mtn, I cancelled 1 and I got a phone call from them saying I owe them 6400 not long after that I received another phone call saying that I owe them 11500 and something I just put the phone down I cancelled 1 contract and when I went into the branch to sort this out they tell me that the money that I paid to cancel the 1 contract they used for both contracts not my problem I wanted to cancel the 1 now I owe 11500 in no time is this how u guys make ur money? It's ridiculous please make sure u fix this because now I'm sitting in a mess I especially told the person over the phone to cancel it, y don't ur staff explain properly or do you just train ur staff to lie to customers...plz sort this out bcz it's a year later already my 3600 went to waste bcz no contract was cancelled...