Unauthorised removal of money from my account.

I recently went away overseas and had enough money in my account. Whilst away I received an email from my insurence company stating that my debit order was returned. Knowing there was enough money in the account I couldnt understand. When I returned 2 weeks later. I did a statement. Standard Bank had debited my account of R13000 for an unknown reason. This meant that all my debit orders had returned. Thus costing me a fee for every transaction. I recently had issues with their pathetic service with my credit card too. They dont communicate when they have all your contact details.