Breach of contract/non existent customer service

Signed a contract for 50gig daytime data and 50gig night time data on 17th July 2018. Eventually received pro data data on 25 th July but charged for data from 17th July and money taken from our account for data not received. Overcharge raised and screen shots provided but still no resolution. Also found on 2nd September that the night time data was not being used when streaming at night. Screen shots taken proving shortfall and provided to MTN. Still no resolution. We have driven to MTN liberty mall, phoned them, emailed them advising their breach of contract on need for resolution immediately. Still no resolution. We are suffering financial loss through maintenance of back upTelekom account while resolving, driving to Pietermaritzburg and money taken from our account for services not rendered. Feedback from MTN liberty mall is almost non existent.This is totally unacceptable. We have spoken to the manager Shane, his I2 Nosi, sthembele the sales advisor and various other employees. How do we resolve? It's almost 3 months and no resolution.