Is my phone with a straight talk Sim considered unlocked?

I bought a Motorola Atrix 4g and put a straight talk Sim card in it. Would my phone be considered unlocked, AT&T, or Straight Talk? Or a combination?

I bought a Motorola Atrix 4g and put a straight talk Sim card in it. Would my phone be considered unlocked, AT&T, or Straight Talk? Or a combination? Or would it be considered unlocked without Sim card, and not with?

or:I bought a Motorola Atrix 4g and put a straight talk Sim card in it. Would my phone be considered unlocked, AT&T, or Straight Talk? Or a combination? Or would it be considered unlocked without Sim card, and not with?

or:I don't think it's considered unlocked, as far as I know a phone is considered unlocked when it is compatible with any carrier anywhere, for example, if I bought a cell phone from Japan and had it shipped to me and they told me it was an unlocked phone, then I should be able to sign my Japanese cell phone up with any carrier in America even though it's from Japan, in reality a sim card is a sim card no matter who makes it, they all do the same thing, store info, so your phone is still an AT&T phone, you just have a sim card in it, I have an Lg phone from Metro Pcs with a samsung sim card in it but it's still an Lg phone from Metro, I hope this helped.

Tags: