HTC Desire - Is it unlocked ?

[Guest Kev75]

Hello everyone

Im new to android and have just bought myself a second hand HTC Desire ( it didnt come with a box or any instructions, just a charger and head phones ), i was told it is on tmobile and that they would not accept it back if i got it unlocked.

Im on O2 pay as you go and i thought lets just try my sim in the desire and well it worked ;)

So now im not sure if this phone is locked or unlocked or what network it was bought on, is there anyway to find out for sure or should i just assume its unlocked as my O2 sim worked ?

Thank you for any help

Kevin