How to tell if a phone is locked?

[Giver]

Are all iPhones automatically locked when purchased through a provider? How can you tell if an iPhone is locked? Other phones I have had show the providers logo on start-up but not my iPhone?

 

[iGaz]

All iPhones are locked to the provider you get them from.

I don't know how it works in the US because as far as I'm aware you can't buy an unlocked phone from there. Here in the UK you can at the apple store...