Debited extra money & doesn't answer their phones

They phoned me with an offer to take a tablet and I told them I don't have money for it but I will ask my mom if she's interested. They said someone will call to confirm whether I still want it, so they did eventually and I told them that my mom doesn't want it and I can't afford it so it's a no on the tablet. Suddenly R140 EXTRA gets deducted from my account. Then I try to phone and I get no answer. Spent 2 hours waiting on the phone now and only got through to another department, who transferred me again to somewhere where no one answers. This is frustrating.