Charged too much and call dropped numerous times

So this month is the last month of my contract with Nashua Mobile / Altec Autopage. I originally signed a contract with Nashua Mobile on a deal that caps my internet usage at 2gig per month. And every month for the last 2 years my account was exactly R399. Now, all of a sudden, my account is R1,685. How is that possible? I'm sure it's just a small technical error.<br> <br> So I phoned the call centre, only to have my call dropped 3 times.<br> <br> Please contact me to resolve.