Over charging

We have always been with Nashau Mobile, absolutely zero problems with billing. What we agreed upon for our cellphone contracts is what we have always paid. Then Nashau mobile was taken over by Mtn. Get our first bill..over charged..second bill over charge...third bill overcharged...absolutely ludicrous. We have called several time to query this and have been promised several times that someone would get back to us..they never did. So today we decided to go in to the store, for the second time I might add, to sort this out. The consultant who helped us bluntly said we would never \see a scent"from Mtn and that the customers are not right. She continued to say that Mtn's takeover of Nashua was not their problem and that they never received the contracts we signed. She also said that my Top up 50 CAPPED contract was not capped and after a point the bill just ran sky high"