Systems not responding,balance increase after paym

I went to pay my ACCOUNT,FIRSTLY I asked for the cashier to print a slip for me so I can check what my balance aswell as the payment due was . On this slip it showed my balance were R817.84. and payment due R35 . Then I paid R200 . as I walk out of the shop I saw that this slip show that my balance is R917.84. When I complained because how can the balance be more after I paid more than i should have,they put me on the phone with head office and this guy told me that my balance is R917.84. after the payment and that the store system is incorrect . so what I want to know is how they do business if the branch and head office system does not correspond . its pathetic.