I'm not happy i want them to alloacte the payment of R290 to me account

I'm not happy with RCS credit card, in March 2020 when the locked down started I have not make payment for the month due to the locked down, the call center called me and gave me options to pay my account I requested the easy pay point and they sent me a reference I must use. I made the payment at Shoprite with the easy pay reference number *** that was provide to me via sms, I made the payment on the 18th April 2020 with the amount of R290.00, the begging of May 2020 the call center called me saying my account is in arrears and I have advise them that I have paid in April 2020 they have not received the payment because they have sms me the incorrect easy pay reference number. now my account is in arrears with R371.00 I sent them a email on the 15th May 2020 and I ask them to allocate the payment I made of r290 on the 18th April 2020 to my account and gave them my correct easy pay reference which is *** and they still have not and now it affecting my credit.