listed on credit beareu as a slow payer

I opened an RCS account with coricraft. They promised the account was 6 months interest free but on my statements they charge interest and other fees, none of this was stipulated on my contract. This is false advertising saying interest is free while they charge it without the consumers knowledge. I decided to pay off my account on the 23 November and I did. I called the call centre to follow it up and sent documents for my account to be closed to my surprise, the payment I made at Coricraft Brooklyn had not appeared at RCS records. Instead of helping me the call centre agent said I should go back to the store I paid and enquire. I did that and they promised to sort it out. In December I received an sms from RCS to pay my account as it was in arrears and I was listed as a slow payer. I went back to the store and they promised to sort it out. I received another sms today that im defaulting on my payments again n im listed as a slowpayer again.<br> I don't understand how this works its frustrating me as a consumer because I have paid my account in full, why must I be a slow payer to something I don't owe. The service at Coricraft Brooklyn and RCS call centre is ****.<br>