Very Bad Service

We have been with Cell C for more then 15 years and this is the tipe of service we recieve... We have 6 contracts with Cell C 3 cell phone and 3 data contracts. About 4 months ago all our data contracts expired, we then decided that we are not going to renew it we would rather go for more expensive phone contracts with more data. So we phoned them and they asured us all is in order the data contracts will be cancelled so we were happy and it was easy, end of the month came and nothing was done they debited our account for the data packages again , we then sent them a email and phoned them again , once again they assured us they will do the refund and they wont debit again , again end of the month came they debited our account and no refund. This has been going on for 4 months and we dont know what to do anymore. This is very sad as we have to move networks just to get them to stop debiting our account for nothing.