Vodacom not refunding overpaid contract because maths is hard

I have a 24 months contract of R138 per month. To finish paying the contract in advance I paid R300 per month. Now I realize I overpaid for the outstanding months.

On the 9th of September: I asked vodacom to refund me the difference between the outstanding 8 months and what I have paid.

Today I followed up and the person says he needs proof of payment for the refund. The request makes no sense as I have paid a little bit more every month so the refund will not match the amount that needs to be refunded me. Logically the accounting department will not be able to reconcile the refund to any amounts on my bani statement.

Vodacom needs to use its brain to resolve this instead of ticking boxes that are irrelevant.

I asked the consultant to ask the accounts department to call me and he says he can't.