CHARGING FOR PAID UP HANDSET

Nashua mobile transferred all clients to MTN in 2014. I upgraded my contract with MTN on 20/02/2015 after my previous 24month contract had elapsed.The amount signed for was R649 on a 24 month contract. March statement had admin.fees and was R893.99.April statement I was charged R789. On 5/5/2015 I went into the Eastgate store and was attended to by Reuben who identified I was being overcharged for H/W fees from my previous Nashua contract of R140 per month, a reference No.USB *** was given with a 21 day period solution.<br> May statement I was charged R771.81. I called 808 who claim Reuben needs to sort out as he gave the reference but Reuben is nowhere to be found trying to call 808 but no answer.<br> How is MTN allowed to deduct these onerous charges?.I need my refund urgently.<br>