my money to be credited back to my account

I had MTN contract for 4 years after those years I have decided to close that contract which was expiring in July 2017 and which I went to deposit the money at the ATM and I send a proof of payment to ********** the ref ********** 6. And Iwas debited and of August of wich they thought I didnt pay my account. I called MTN call-center several times to , I spoke to 1 of their agent by the name of Itumeleng and she gave me a Ref : 1- ********** 2824 for my query because my number is no longer on contract and the ********** 23 is a ref for the call. I have been calling MTN almost every week for my money to be credited back to my account. All references for my calls are : ********** 80, ********** 07, ********** 45 in all these REF they haven't return my money which is R350 the number that was ********** 949 has been cancelled out of contract as I requested NOW its on prepaid. I want my money back now, or I will follow legal action. The last agent I spoke to was Nhlanhla and he assured me that he has resend this query to accounts department