Disgruntled customer

Ist of April I paid R2000 upfront on my cell c contract account but I used a wrong reference (my old account no).I realized my mistake and I contacted cell c to explain what happened I also emailed them proof of payment.The following day I received an email from them informing me that the amount has been allocated accordingly.But to this day the money has never been allocated they even debited my account end of April.I have been calling their customer care for more than a month now ive gone to their physical store iv sent emails but still nothing.I made an upfront payment because I want to pay up my account and take another phone. Iv been with cell c since 2008 as a loyal contract customer but this is how they treat me.