Vodacom charging us for upgrade that never happend.

Vodacom are charging us for an upgrade in September 2017 that never happened! We have spoken to the branch and have had no logical explanation. We have spoken on a few occasions to the accounts department without any positive response. We have stopped the stop order payment as they want to ***** R400 from us. this is happening every month from September 2017 to date and we are now at wits end. and we still have the poor data speed that we have complained about years ago and where told a bunch of lie's