Disgraceful service.

I downgraded my package on the 15th of June jus after I made a payment of R640 and moved to a lesser package which was confirmed by them that I will be paying R358, on 15th of July they deducted an amount of R400 which I believed to be inclusive of insurance for 2 decoders as agreed. Now they say I owe R893 and disconnected my services. An I am told to first pay then if there was a mistake on their part they will "gladly refund me". Some consultant is now telling me that it might have been a system error or there were no funds in my account which is bull-dust.