Double debited

I've been calling Mtn since last week Tuesday and every time my call gets disconnected or I'm holding to be helped for more than an hour, my account has been double debited I was told that I should wait 3-5 working days before the refund will be done.

Today I called again in hopes that the money will be paid back into my account because I have debit orders which are now pending and that's making my account be in a negative, now I have to wait for an additional 21day which means I should be getting the interest that my money will be accumulating as well right? I'm very upset with the treatment and service that I'm receiving from Mtn, can you guys please advise me on whether I will get my money tomorrow or not!