Poor Customer Service

If I could give zero stars out of 5 I would. The worst customer service I have ever experienced.

Made a 3rd party payment at my local Builders store to my Builders RCS credit card on 9 November. it has not reflected on my account, yet the money went off and I have my store slips as proof... for 6 weeks I have been hounded constantly by RCS call agents saying my account is in arrears and I emailed and Whatsapp'ed proof of payment and still nothing has been sorted.

RCS have taken more money off me in late fees than what the instalment was valued at and all I did was go into store and make a 3rd party payment at the right date and no RCS representative can help me- 6 weeks on.