Telkom ****med me

I have a cellphone contract with telkom, last month they debited R200 more from my account. When i called them to find out, i was told it's a fee i have to pay because the previous month the debit order was rejected due to insufficient funds. When i took the contract 3 years i go no one told me about this and the sad part is that I've never skipped payments in the past, not even once. So i want to say shame to telkom and your staff for not disclosing this information to your customer