MTN not crediting my account after Mondo(MTN) slip up

I have returned a device that was sent to me by Mondo(MTN), being the incorrect phone. After struggling for a month to get that phone off my name, and reverse the upgrade to go in store rather, Mondo then just cancelled that contract and did not credit my account, after phoning multiple times I was assured I will not be billed due to requesting a return in the cooling off period. But as guessed, Mondo did not request a credit, and for a month I have been calling and waisting Airtime to try and get them and MTN to credit my account. Over the weekend a sum of more than R12 000 was deducted from my bank sending me into debt. I do not have any funds to pay rent, buy food or even to pay for petrol to get to work. My bill to the facts should have been R660 , not this large ammount. And when MTN tried to query this, Mondo responded saying my account was credited....I have been phoning both these companies non stop for over a month, and there seems to be no resolving of the issue, why would the company have them as a partner if they can not work as one?thinking I must go to the ombudsman and radio talk shows next. This is complete fruad.