Even the manager is *********** and unprofessional

I have a billing error with my mtn account. This happened 2 months ago. I've been going back and forth to the store to rectify the error. I was told that the manager would call me but he didn't so I had to go back to the store. The manager assured me that he will sort the issue out asap and I would be refunded immediately thereafter. I called him a few times to find out what's been happening. The last time that I spoke with him, he said that it should be sorted out the next day and I would be refunded the day after. This was over a month ago. I've been trying to call him before the end of last year and he wasn't taking my calls. However after I tried calling him, I got an sms from mtn acknowledging my query. Over 2 months has gone by and no refund. I don't even know whats happening and how do I find out? If I go to the store, they will say to me that the manager isn't there, If I call the manager, he won't take my call. If the manager of the store is so *********** and unprofessional, how can the staff be any better? Just about every dealing that I had with that particularly Mtn store was a disaster. I have 2 contracts thats up for renewal and I'm not going to renew them. For clarification purposes, this mtn store in Northgate is the store outside the mall, next to the Virgin Actice. The store mangers name is Gavin.