Can't correctlt return goods if account paid off

I bought a kettle 23/06/2015. It is under guarantee until June 2016. It stopped working and I tried returning it to JetMart on Oxford Street East London. The departmental manager Eric told me on 04/02/2016 that it is problematic to exchange it as I had paid off and closed my account, so I should return the next day so he can call his helpdesk for assistance. I returned on 05/02/2016 and spoke to someone telepathically who told Eric to make a decision regarding exchange. Eric then said the following due to the fact that I had closed my account a cashier can't help me so he will do me a \favour\" and just give me a kettle which I can't later return as I will not get a slip. Furthermore I would get a kettle worth R99 as opposed to the original price of the kettle which was R139,99 because the kettle was on promotion when I bought it and I got a promotional discount which reflects on my slip. I asked if I can't add money to the R99 so I can get the same kettle, he said no since I'm not getting a slip. Is this correct that a loyal customer who pays their account on time can't make exchanges due to closing an account?"