Solved an interesting problem tonight. I had an old AT&T Z221 phone, and wanted to migrate the address book from the SIM card to a new iPhone. The AT&T website had a support page with information about copying contacts to and from the SIM card. Still, I had no idea how to transfer that data to the new iPhone. Furthermore, the AT&T Z221 phone I had on hand had a busted screen. It would have been impossible to navigate through any menus on it.
From Apple, I found a support page on importing contacts stored on a SIM card. I knew that the iPhone 6 would have a different sized SIM card than the AT&T Z221 phone. So, I popped open the SIM card slot on a three-year-old iPhone 4S. No go. The iPhone 4S SIM card was too small. Thankfully, I still had a five-year-old iPhone 3GS on hand. I had to search a bit for the SIM card slot, which was located at the top of the phone. This time, the SIM cards matched.
For the final step, I signed into iCloud from the iPhone 3GS. After importing the contacts, the sync was instantaneous. I checked the new iPhone 6 and the contacts matched the address book of the old cell phone. Success!