Mr Price online - Double billing - Balance owing cannot be justified

I have a Mr Price account, which I paid up need of June and had only purchase air time to the value of R250, together with an on line shopping I did last week to the value of R550. On the 1st of August, I went to the local Mr Price home to pay account; only to find that instead of the R800.00 I know myself to be owing account balance is nor R1 400, it has double up. Something similar happened a couple of month ago, when using the Mr Price on-line function. The store agrees with me that the numbers do not add up the balance does not have any support and cannot be justified. I have now been tasked with having to call Mr Price myself and the ********** ; just ring off the hook. Very disappointed and I expect this to be sorted out and also for double verification on all the online purchases double billing.