Refusal to change my banking details

I closed my bank account due to unauthorized debit orders and when I called Telkom call center to change my banking details I was told they cannot do so as my account is less than 3 months old, the lady I spoke to advised me to pay via Easypay and I have been doing so and never missed any month ..But now my profile is blocked and am told I owe a chunk of money for rejected debit orders regardless of the fact that I have been paying on their advise.