Installments

I joined the gym for my girlfriend and I've been paying my installment through debt order from December 2014 until August when I stopped the order and I asked for an account number that I can make payments in and they gave me this Account numbers :FNB *** I have been depositing my monthly installment of 200 in it I'm surprised now that I've been handed over to lawyers saying I haven't been paying and the last payment I made was in December I'm very unhappy with this because I was paying all this time.