Cheaper rates = low quality connection

I changed mobile service providers approximately 2 months ago - my biggest mistake ever. I cannot seem to find a single call centre agent who understands billing issues or the fact that the quality of calls is pathetic. Besides my calls being dropped regularly, the quality of the connection is so bad that both me and the person to whom I am talking can only hear bits of the conversation. I have tried explaining this to the call centre agent, they claim its settings on the device. I have changed settings according to their instructions to no avail. May I please advise any other person thinking of switching to TELKOM MOBILE: Please DO NOT - their rates are cheap since their service is even cheaper.