Unreasonable March 2016 account - Ref 336833

The service provider included a R700,00 increased deposit amount into my 11 March invoice no.***. This is unjust ANDWOULD LIKE YOU TO INVESTIGATE- I WONT PAY THIS AMOUNT. The consumption amount for period 13/01/2016 - 12/02/2016 is R388,36 . The amount due now is R1,129.55. THEY REFERRED ME TO ARTICLE 17 OF THE CONTRACT and I have argued with them that I did not default on the February 2016 payment but they maintain their system did not understand from whom the deposit was from as it had REF REF before the account number 336833.