WHY?

I'm so tired of Old Mutual, its the same story every second month. Trying to double deduct my account and then sending threatening texts to me. I have an agreement to pay R668 every month on the 7th of each month. I have not defaulted on my end of this agreement. This month for some reason they deducted that amount on the 1st and the 2nd. I reversed the amounts since my debit order is for the 7th. After I reversed the money I got a text saying the amount of R1,200 did not go through and therefore I am in default and they will deduct R300 extra a month to make up for these arrears. Since then I have been bombarded with text messages threatening to hand me over to the legal department. WHERE IN THE WORLD did we agree that I would pay R1,200 a month and/or give permission to double deduct????? I have a signed agreement stating R668 on the 7th!!!! Yesterday was the 7th and the amount of R668.20 was successfully deducted and yet I now just received 2 texts stating that I am in default and will be handed over for summonsing???? I have emailed but have had no reply whatsoever. I'M FED UP!