Migration not implemented and nobody cares at MTN

I exceeded my data usage on my 3G/LTE router and decided to change my contract to what MTN calls a Top Up contract, which cuts off your internet completed to prevent the exorbitant out of data bundle rates of 99c per MB that MTN charges. Phoned the call centre, spoke to Tatum Love on 24 June and completed the necessary paperwork. Communication was via email and I confirmed the she received the documents the same day and also she confirmed the contract migration will happen on 7 July. Only to find that my next data invoice was for R6800. I then called 808 and spoke to a new call centre agent, Themba Hamnca, who told me Tatum is not working for MTN anymore, upon which I asked him to escalate my issue because why should I be held responsible for MTN's mismanagement of work. All communication to Themba is currently being ignored by him, leaving me in the dark. I tried again to phone the call centre to try and speak to a manager, but my call got dropped after waiting the line to speak to a manager after explaining my soppy story to a new call centre agent. Nobody is phoning back and MTN clearly doesn't care about little old me who has been a loyal client for 18 years.