Missing payments

On 19 August 2015 I paid R 5000 and on the 25 November 2015 I paid R3000 using my store card, account no: *** <br> What worries me is that since the 09 December 2015 the shop has been asking me to make payment, they say they didn't receive the money but I have proof thathat the money did went through, I have taken this matter to the shop management but everytime they tell me that they are still investigating while they expect me to pay,please help because this may ruin my credit status.