I've got 2 sim cards from diferent carriers (work & private) & my treo is unlocked so I can use either.

My question is can I just pull out the sim card & stick the other in while the phone is still on, or should I power it down or something - couldn't find anything in the manual.

I've done it a few times & it just turns wireless mode off till I manually turn it on again, but I'm wondering if it's going to cause any harm to the phone or the sim?