Still being billed after end of contract

Took out a cell phone contract in 2010 with Virgin Mobile for the period of 2 years which was standard at the time for any mobile network company.This was done over the phone. Its was for the amount for R100/month.When i received the cellphone it wasn't activated.I then took the phone to Virgin Mobile in Pavillion to activated the handset ,they could not help me to activate the phone.I ask the sales consultant if i would be billed month end if the handset wasn't activated.She told me that they cannot bill me without an active handset. I've never used the cause it was never activated only to find that they billed me up to now for a contract that was never in use from 2010 and should have ended in 2012.i only picked this up when I started doing internet banking,cause an amount of R100 does not appear as a debit order on my current phone.i went to the bank to query the debit order and they gave a a contact no.I phoned them 2 months ago to find out about this debit order and was told i need to cancel the contract which i did only to find that they increased the monthly debit this month to R500. This to me is unfair practice and would like my money back for a cellphone never used.