Pay back my money please i beg

I had an account with builders which trades under RCS, they claimed that i did not pay them for 7 months of which i was paying and i proved it to them. 2 years later they admitted that the fault was on their side and that they will allocate those payments until today they never done that, as a result i was reported to the Credit Bureau which now restricts me from getting loans etc. RCS owes me over R12000 and they won’t reimburse me.