MTN won't Refund me my credit!!!

I have tried for nearly 6 months to get MTN to refund me over a R1400 rand that is sitting in a credit with them on my two profiles. I have been into 3 different stores of which no one can help. I have phoned countless times to no avail. Always getting transferred to the wrong department after holding on for 45 minutes. I have sent countless emails again the keep asking for the same thing proof of payment which I have sent so so so many times. Could you help me get my credit that is due to me. I am ar my wits end? It is ridiculous that one cannot speak to anyone and that no MTN store can help! I am fed up with MTN.