can the sim card of a pantech link 2 fit in the iphone 4 or 4s

The iPhone 4 and 4S take a micro-SIM. You'll have to find out what size SIM the Pantech takes. Even if it will fit, I don't know whether a SIM not from an iPhone will work, though you could try it. I'd suggest you just get a new, proper SIM from your cell carrier.

Regards.