Apple has posted a Knowledge Base article on swapping SIM cards in iPhone, which the company says may be required for

“repair, warranty service, or if you own an authorized unlocked phone (Germany and France only) and want to use a different network provider’s SIM.”

Apple basically states that your SIM card can be swapped, however the user should immediately connect the device to iTunes in order to insure proper operation.

“If you do not connect iPhone to iTunes after changing or reinserting the SIM, iPhone may not work as expected.”

Any other questions? Check out the article here.