You would probably be better off doing the following @mark.lew1975:
- Pick up a PAY GO SIM from another network
- PAC out your iD Mobile number to that PAY GO SIM (A Final bill will be generated)
- Purchase a new iD Mobile plan (you get a better deal as a new customer)
- PAC your number from that PAY GO SIM back to your new iD Mobile plan
- Pay your final bill from your original iD Mobile contract (includes the early termination fee)
You can, of course, request a replacement SIM or use your old one in your new device until you're eligible for an upgrade on your existing account.