Unauthorized double debit

I made an arrangement on the 18th to pay R630. I was later contacted by a lady and told I'll need to pay an activation fee of R150 and then I'll have an option to select a payment that's suitable for me but today 2 debit orders of R1093.75 each went off, a total amount of R2187,50 went off my account after I made an arrangement to pay a specific amount and it's not even my money. I called in after the first debit order and I was told I'll be contacted back but instead of that another debit order went off. I need urgent assistance.