Over R2000.00 debited from my account

On 24 Feb 2015 I received an sms that Mtn will debit R2376.73 from my savings account on 27 Feb. I did not receive a statement for this amount (still haven't). I used to be with Nashua Mobile before they closed down. I called in to query the amount. The call agent stated that they do not have any proof from my records that I have a usage limit on my account. He stated that he would escalate this and they would call me back within a few days and gave me a reference number. After 5 days have passed I called in. The new call agent contacted the Nashua Helpdesk. I over heard the conversation and the Nashua Mobile agent confirmed that I had a cap on my account (so I shouldn't exceed the amount of R500.00pm). The Mtn call agent asked that the details be sent to her so that Mtn can bill me accordingly. She gave me a reference number and said I should call back in 48hrs. When I called back the new call agent stated that the situation has to be escalated to Nashua Mobile and that there is no proof that I had a usage limit with them. I asked that she should email the original call agent that worked with me and have the agent call me yesterday. No one has contacted me yet.