According to iPhoneatlas, an improperly seated SIM card can impact iPhone signal strength. Ejecting and then re-seating the SIM can sometimes resolve the issue. If that doesn’t work – try the following at your own risk – placing a piece of scotch tape on the outer side of the SIM card holder increases the pressure on the SIM card contacts and thus improving signal strength.
Check out iPhoneatlas’ other tips for improving iPhone strength.
Grew up back East, got sick of the cold and headed West. Since I was small I have been pushing buttons - both electronic and human. With an insatiable need for tech I thought "why not start a blog focusing on technology, and use my dislikes and likes to post on gadgets."