If putting a foreign SIM in a phone that is locked, it will either say "Enter Subsidy Unlock Code, Wrong SIM, SIM Error," or some other message. If it isn't locked, then it will continue to go to the home screen like it would if it had the carrier provided SIM.
An un-activated SIM would either get "No Service, or some other message. A previously activated SIM that is deactivated would say " No Service, Emergency Calls Only" and some show an icon with a phone with a slash across it and some show reception bars that are greyed out.
If you don't have a foreign SIM to check with, depending on the phone manufacturer, some have a secret code or toggle combination that displays if the phone is subsidy locked or unlocked.
On some GSM Samsungs, typing *#7465625# displays the locks that are enabled/disabled.
From another thread titled GSM Phone unlocking FAQ Post #7 discusses how to do it on some SonyEricssons to display the phone locks enabled/disabled.
Originally Posted by AdmiralAK
If you feel that you have to correct some of my posts for my capitalization of some of my words, then just bear with it. It's just a discussion forum where some may be limited by time to answer in well-versed and eloquent sentences.
I already got a PHD (Plain High School Diploma) so ignore my style of writing and I'll ignore your ignorance.
Subject: You can read this-trust me!
I cdnuolt blveiee taht I cluod aulaclty uesdnatnrd waht I was rdgnieg. The phaonmneal pweor of the hmuan mnid. Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it wouthit a porbelm.
Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig huh? yaeh and I awlyas thought slpeling was ipmorantt!
When asked if I see the glass half empty or half full, I responded I see just a glass of water.
Now you know how I think.