Cancellation

My contract has finished and I cancelled my contract with autopage. I received a mail to confirm it will be effective on prepaid 03/06/2015. Until today they haven't switched my number to prepaid and I have spent lot of time on the phone to have this resolved. My data usage have accumulated to a substantial amount cause this client services did not want to load once off data for me and they said it is prepaid. So I have just received a mail to say my limit is almost exceeded. Hence my other contract with them was changed to prepaid the 30/05/2015 already, and both was effective from 03/06/2015.