VODACOM DOESNT WANT TO REDUND ME

A follow-up to what Vodacom has been doing to me. I was supposed to get a refund because vodacom charged me for month of data after I gave them a 1 month notice and my contract was supposed to end. I contacted them many times to sort this issue out and not they did not refund me. Now they sent me this message on IG and want to take a credit towards my account when they were NEVER supposed to have been taking money from me in the first place. Here is the response I got:

"We have loaded the credit for the outstanding balance on the account. The Amount due was R713.66 due to December and January invoices raised, reference number is ***. This will clear your old account with Vodacom as the contract has been cancelled."

This is the most ************* service provider I have ever met or they are acting dumb so they don't have to refund me. Vodacom you owe me a refund. No one has told me this money will go back into my bank account. As far as i understand you want to take my money owed to pay for invoices you werent supposed to be sending. All my contracts are canceled and I owe you nothing because you took advantage of me in the first place. I canceled within my cooling period so dont play with me. Sort the issue out and stop dodging the refund.