MTN Frustration!

I have had a contract with MTN since 2014. Last year due to being unemployed I defaulted. MTN handed me over to a law firm called SSDA. I found a job and made a payment arrangement with them and I paid monthly. October 2017 I requested a reactivation amount which they supp**** and I paid. The account was handed back to MTN and my number was reactivated and I paid like normal again. Then to my surprise on the 31st December 2017 MTN deducted R4700 from my account! Imagine my shock. I call MTN and they apologise and say they don't know what it was for as the account is with legal. I explain the whole situation to them and they say the will escalate my query. In the meantime I reversed the debit order. Two weeks go by and nothing from them. I call again and same story I have to explain the whole situation and they say they will escalate it. I call after two days and still same story. I called SSDA and they say the account has been closed on their side. So now my account is suspended and apparently in arrears and MTN can't help me. I am so frustrated because I don't know what to do anymore!