Worst Service Provider

The Worst Service Provider ever, My wife has a month to month contract for WiFi data, it was initially R460 then surprisingly it’s R580 with no prior notice of the increase. For June she has already paid but there is no data allocated and the router is not working. Now she is told she will only get the data in July despite her paying full amount in June. We want to cancel MTN is refusing to refund us.please help.