Incorrect billing not resolved even when escalated

For a few months now we have had discrepancies with exuberant billing on an MTN account. Account Holder: Pieter le Roux Cell # ***. Since April 2015 we have been receiving extremely high billing and nothing out of the ordinary was done and we had no way to prove that nothing had changed in the usage. In August we went into the MTN store again and changed the package to an unlimited package called the SKY package, for R2000.00 p/m unlimited calls and data, the paperwork was completed by Dominique at the MTN Typervalley store. the next month, there had not been any change in the billing it was still exuberant, we had gone into the store again and tried to sort out with the admin staff, this was so frustrating we escalated to the branch manager. she had assisted us with an upgrade of the contract but still we have not had any joy with regards to the exuberant billing which had been process prior to the SKY package upgrade and the high billing after the SKY package was activated. Going to the Tygervalley store is really a sad affair, you sit and wait forever, no one can help you with your query, you end up going to the branch manager and still the billing was not sorted