Yes, contact your SP to cancel the contract and request a conversion back to prepaid. If you don't know who your SP is ask customer care on whichever network you are on.
If the term of the contract isn't up, you'll have to pay up to cancel, generally whatever the remainder of the contract would have cost. Usually better to let it run out.
First you'll have to cancel the contract with autopage. Do it today cause you need to give a full calender month's notice. Then you can port to pre-paid. Auto page can't do that cause they don't do pre paid. If you wait till the new month to cancel it you'll have to wait till 1 august to port to pre paid so do it today.