Over-charging & Non-compliance to contract

I am getting over-charged since 2 months ago and Autopage just closes calls without bothering to feedback. I spoke to Faizeen on the 11th of September after my previous called logged with Pretty on the 3rd was closed without any feedback. Autopage claim my data bundle that is part of my contract expired 2 months ago and are now billing me for all my data at a higher rate than I contracted for. I purchased a contract at a set price inclusive of 100 minutes, SMS'es and 1GB data. Auopage have chosen to change my contract terms without any prior notice, a contravention of the CPA and law of contracts. The last I heard they were getting my contract to get back to me in 48 hrs and now nothing yet again. Since Autopage took over November 2014, I have battled getting through to their call centre repeatedly and had to repeatedly log call that are just closed without any feedback for (1)my bills that I only got months later, (2)itemised billing that I only starting getting in my last 2 invoice periods and now this. I am fed up and expect a refund for all services not rendered to revert back to my existing contract terms until I am notified in advance in writing of any changes.