Bad Service with ***** Comitted

Looks like there is no one in mtn willing to help. I took out a contract from mtn store President square got good service 2 weeks after that i received an email that stated my numbers was changed as per my request and the attached documents was signed by client signature and it wasnt me. The sales agent made a mistake and decided to rectify it himself and signed for me which i see as ***** was done without me knowing. I sended an email to mtn ***** mail and got a response i must mail pinnacle marketing. i did receive a call from them yesterday to say they spoke to the consultant and he said he is sorry it wont happen again. To me that is unacceptable if they can change things on my name and sign for it while im not present what else can they do. I want an answer from mtn how this will be resolved i refuse to have my contract by a shop that commit ***** because thats what it is. I will be cancelling my contract if i dont receive results.