Cellc bad service

I'm experiencing a very frustrating situation with Cellc. Their service is very bad. I paid through EFT after a failed debit order but used wrong reference number by mistake now is a struggle to refund my money. I'm working in an environment that doesn't allow phones . They told that they have to call me before refund if I can't answer a phone I can't get my money. I never thought such a big company can behave so poorly. My contract number is ***