How to check my iPhone is not locked?

Check Carrier Settings

The simplest way to check if your iPhone is locked or unlocked, is to check your carrier settings, tab your ‘Settings’ on the home screen, then look for ‘Mobile’ or ‘Cellular’ tabs(if the device is set to American English, it will say ‘Cellular’ instead), then check for the option named Mobile Data Network (or Cellular Data Network). If you see an option of Mobile Data Network, then your phone is most likely unlocked. This option should not appear on the locked iPhone, however you should also recognize that this method is not 100% reliable. To make sure, you can double-check by ejecting your SIM card and shut down your iPhone, and when reboot your iPhone, make sure the carrier status says ‘No SIM’ or ‘Service Not Available’, then tap ‘Settings’ once more, if the ‘Cellular’ or ‘Carrier’ option is still available then your iPhone is unlocked.

Read more:https://www.etradesupply.com/blog/how-do-you-know-your-iphone-is-unlocked-or-not/