I bought a used iPhone 4S from a second-hand phones retailer here in Egypt. He said the iPhone is Factory Unlocked, we tried my Mobinil SIM and it works fine, I have no other carriers SIM that is already working, I tried another carrier's SIM that is already suspended and the iPhone goes "Searching" then says "No Service", it doesn't say "Invalid SIM".
I found some IMEI checking websites, but some say it's unlocked and others say it's locked. So, Is there any way to be sure if it's Factory Unlocked or not other than trying another carrier's SIM ?
Thanks In Advance. 
