Can an unlocked iPhone 4 be re-locked?

[MacInTO]

In March, my iPhone 4 died recently and my provider sent me a new iPhone. My previous iPhone was jailbroken and unlocked because I had one of the unlockable modem firmware versions. However, my new iPhone is on 03.10.01 and this is not unlockable so I didn't even try.

I live in Canada and AT&T is not my home network. Recently, I went to the US. When I was there, I though I would try my AT&T GoPhone sim card. To my surprise, it worked!

I'm currently on 4.2.1 and firmware 03.10.01.

I'm wondering if I update the software, could my phone be relocked?

 

[rgarjr]

Your phone is not unlocked right now. if u want unlocked get a Gevey.

 

[MacInTO]

Your phone is not unlocked right now. if u want unlocked get a Gevey.

It works on two different networks - one in Canada and one in the US.

 

[MacInTO]

My phone came from the carrier unlocked.

I want to Update my iOS to 4.3 from 4.2.1. Do you think it will lock my phone?

Anybody have any thoughts on this?