Poor service, over-billing, bad attitude

Been a client since 1998. 2 Gig data contract + iPad. In 24-month period I never used all the data nor exceeded it, data was always carried over. At end of contract term I'm now billed for short messages - R2.57 (impossible on iPad) & PSD Calls (R1387.77) above the 2 Gig pricing when I've not increased my usage. I cannot understand this, it's as if I'm billed on contract & out of bundle or else your network has allowed someone else access to my number. Queried 1 Jun '15 - still no response - ref ***. More emails sent re this - no satisfactory response or answers to questions. Call center doesn't even listen to what your trying to explain. Keep telling me that sim has been in a phone the more I explain it's been in iPad since I got it. I have turned my cellular data off on the iPad since 31 May because I'm too scared of getting billed even more. So in other words this sim is useless to me. I was thinking of getting 2 more data contracts but now I just want to cancel this sim and I will probably do the same with my other lines when their contracts expires at the end of this year. To think that I once bragged to others about your good service. I'm deeply disappointed.