Refund Nightmare

I have had a data contract with Cell C for over two years. I am on a 2Gig Postpaid contract for R99, meaning that I get billed a month later for my usage. My contract ended 28 January 2015. But my nightmare with Cell C's billing started in December 2014 already. I checked my debit at the end of Jan 2015 for usage of Dec 2014, I was billed R279, instead of R99, a difference of R180. I got credited after I questioned this, but in Jan 2015 my account was messed up again. They could only charge me more pro-rata as from 29 Jan, but again my account was charged for R279, plus some extra usage I had, instead of the R99 plus extra usage. So again I was overcharged by about R150.00. <br> <br> I have called countless times, I always get promised I would be called back, within 2 business days. It has been escalated every time. Still no result!<br> <br> I want this sorted ASAP!