Poor service at Autopage

I just upgraded my contract now on the 08 of February 2015 and I got a new S5 phone on a my choice 100 package. The problem now is that I'm being changed R407.56 extra unbilled charges on my statement they say its my data usage from 17 February to 19 February. As my package is a top-up how can I have unbilled charges Its just doesn't make sense at all now I they say I'm liable for these charges I'm really not impressed with service I got and after I queried this they never even gave me feedback I had to call them over and over again to get clarity on this.<br> <br> Please help this just doesn't make sense because now my March 2015 statement is R793.05.