MTN Service Sucks- Trying to Rip me off

My MTN contract came to end on05/05/15, I recieved a bill from MTN that i'm going to be charged R170 compared to me normally payin R69.00 per month. I called call centre on19/05/15 to query this bill and the Staff member Tandiso advised that my contract ended so now my discounts fall away and i'm liable for R170 i then immediately requested that they move me to Prepaid and reverse the charges, he confirmed that he will request i get changed to Prepaid and would take 48hrs and retentions would call me but i'm liable for the cost. I then requested for his team leader Yongama to contact me as i was not once notified that once my contract end the discounts will fall away an i will be liable for R170 to make things worst i was not contacted once by retention to offer me a renewal even though i contacted MTN few weeks ago to query how i can port over to Vodacom as i'm not getting proper service from MTN. Yongama advised that she will reverse my airtime that was loaded &i wont be liable for future bills but my account will b change to prepaid on 21/05/15.Checked with MTN store on23/05/15advised i'm still in contract.Now my complaint is delayed due to the MTN striking call centre is closed