Unauthorized Debit Order

We have been trying to call 808 to no avail for days now. I upgraded to a S6 Edge about 2 weeks ago. There was NO ****EN OUTSTANDING money on this account or we would not have been able to upgrade. The lady at MTN showed me the account was in standing order. Now today they have deducted R1185 from our account FOR WHAT IS THIS EXACTLY??? As out debit order is set for the 15th not the 7th and when we go to the MTN store they tell us they can't see anything on the system. Please return this money TODAY as we have been paying this account all the time. This is unacceptable and the fact that you simply don't answer your phones makes me wish I never upgraded to the S6 so I can cancel this account.