Billing me the incorrect amounts

I have contract cell phone with MTN, they have to deduct me R249 however for the past few month they have been deducting more, when I asked they said I registered something to get extra data which they were lying cause I know I didn't sign anything. however I asked them to remove the extra staff and didn't ask for my money back. this Month they deducted me R259 and I have been trying to call and they are not picking their call centre phone. I know <br> <br> These people trick people, my friend was also complaining about bad service from MTN. I had an issue with them last year when asked them change my debit order and they only did it after 4 month. Now I need my money. their sitting there not doing their job properly and I am not sure if they are qualified or what. I am tired of their bad service. they cant treat customer fairly and forget they make revenues by us.