Poor Service to Loyal Clients.

I have been a client with MTN for almost 10 years and have been paying my MTN account via EFT. In March I paid my account as I always do but they did not allocate it correctly because of a system upgrade. It has been 2 months now that I have been struggling for them to do it because each Month they cut my lines due to non-payment and now they want to give me the blame. Every time I phone all they say is it will take up to working days. I have sent multiple proofs of payments to them and every time I phone the call center they just ask for another one.