wrong amount and gigs added with no authorization

Hi. I was debited my instalment at the end of June 2015. Which was R1427.00. My bill normally averages R688.00 . I contacted the guy at autopage shop. He checked for me and saw that i was billed for 5gigs data and pro rata( 1month) he then asked them to pay me back which was almost 2weeks ago. I spoke to the accounts department yesterday and they then said to me that the only need to give me a 300 back?1427-300=300? That's what i was thinking.. I was told i have to wait 7days again for my money. My argument is how to they just manage to add to my account without my authorization? All my sims of my contracts have top ups. They so quick to take money but take so long to give it back. I then did a reversal at my bank and paid them R700. Waiting to see what happens this month.