paid installment reflecting unpaid

I paid an amount of R50 towards my Hub account at the Phoenix Plaza branch on 20 February 2015. After that in March I have received numerous telephone calls from Nedbank Collections dpt informing me that my account is in arrears. I informed the Admin that my account is paid and is up to date - I was asked to fax the proof of payment to ***, which was faxed on 12 March 2015 to the Admin dpt. After the 13 March 2015, I am now receiving numerous sms informing me that my instalment is still unpaid for February. I informed the Admin dpt that my payment slip of R50 for February reads \Sale Transaction"on top of slip instead of Payment tranasction. The name that reflects on the slip that received the payment is \""Naidu G\"" at 11:42am on 20 Feb. I would be greatly appreciated if the Admin of Hub could update their records as soon as possible."""