unlock iphone

TexasJJ wrote:

I have two old iphones that are not currently on my account. Can they be used with other carriers

How to unlock your iPhone for use with a different carrier - Apple Support

If they are unlocked then they can be used with any carrier.

TexasJJ wrote:

I reset to factory default but how do I know if they are unlocked.

You click on the link I provided and follow the steps.