Multichoice is a nightmare

I am on price lock for 24 months and my subscription amount is R518 per month but multichoice messed up my account when I won free subscription on the DSTV rewards app in April, now they are telling me that they made a mistake and credited me double, they never called and notified they just kept quiet for those 2 months (June & July) and did reversals on my account and I only noticed that they are triple charging my account a week before the debit order goes through on the 1st of August. Now I am expected to pay for 3 months subscriptions at once like it is my fault that they made a mess of my account.