Wrong Billing, Bad service. No help

MWeb deducted an amount 6 times more than they are supposed to. They state -after I phoned 6 times I used more data than the 20 gig I subscribed to. Every month my internet usage is cut before end of month. When I called them and they stated my 20 gig is finished, and thus stopped. Now they claim I used more than 20 gig, but it is impossible as they stopped the internet access. I called 6 times this morning. NOBODY can OR WANT TO CANCEL this account. NOBODY can tell me how much data I used up to date.Everyone tells me . Tell me I must log into My account to cancel and see usage. I told them it is impossible for meto log in. They still refuses to cancel or look up the data used. They sent me \passwords"two times"