21 day wait for refund from MTN

MTN promised to cancel my debit order as I want to pay it earlier from my bank, I spoke to a lady and she told me I was still in time to pay immediately and that she would cancel the debit order from their side. well well well I paid them June 25th and they deducted again June 28th. I was told this morning that the refund would take 21 days unless I send them my Bank Statement. I spoke to Amdile Bhodningwe, she was quite rude and she promised me that the supervisor would call me. I havent heard from MTN again, when you are a day late with a payment, they cut you off. Why should I wait 21 days for a refund, which they never informed me of in the first place, I picked it up on my bank statement. Ridiculous!!!!