Return debit order

I call Telkom to update my banking details, the guy I spoke to told me that he has update my account yet yesterday they still tried to debit my old bank acc so now who is liable for the return debit order fee??? I just called their useless call center and spoke to Mapule, she asked me to hold then hung up on me. I refuse to pay any fees because I called and informed Telkom that my banking details have changed.