poor service from MTN

this is regarding my 73 year old mother that did her upgrade online. everything went well until the phone she was sent went blank. she was sent to Canal Walk Mtn. there she was told that an outside firm does the upgrade. to cut a long story short (i have all communication) MTN has now charged her a 2600 cancellation fee when she did not cancel the contract. that was done by a third party company and she went in to MTN to do her new contract as she had been placed on pay as you go.