A new SIM would mean a new account and loss of your goodybag.
You can order a new standard SIM on the same account and keep your goodybag and all other account details from:
This will block your current SIM until you activate the new one.
If you want it for an iPhone 4 you will need to get it cut down.
I wanted to order a new sim and use my number on in how can I do this ? And would this affect my current goodybag in any way ?
Just to clear things in my own mind....
Do you want a replacement SIM because there is a problem with your current one? If so, use the Lost SIM link in Help to report your SIM (but not your phone) lost. Giffgaff will send you a new SIM with the same number and all your credit/payback etc. attached.