Brian7363,
It is not your sim that is the problem. It's the phone being blocked by the network that's causing the issue hence your sim card works in your Sony phone but not the Iphone.
try checking the Iphone's IMEI number on sites like CheckMEND - The Global Second-Hand Stolen Goods Database for Public & Trade Checking, I'm 99% certain their report will confirm the phone is reported lost, stolen or an insurance claim.