ok got my iphone unlocked ages ago and it worked fine on other networks but i then downloaded 3.1.3 on itunes which locked the phone so i went to 02 and got it unlocked again but since then it keeps saying searching or no service at the top any one know what the problem is

 

If o2 have unlocked it legitimately take it back to them to sort it or get them to give you a new one as they've obviously screwed it up. If it was unlocked by some dodgy second hand shop or market trader it's gonna cost and no network will offer support for it. Also if you develop any faults with it due to shoddy manufactorin no authorised service repair centre will touch it as they can tell if it's been unlocked via hackin etc

 

What network are you on?

And as said above if it only started doing that after 02 unlocked it then ring them back up and tell them.
If you have a 02 sim use that to call them as its 35p a call that way, if not its international call charges

 

02 unlocked it the second time only started once they unlocked it

 

Have you tried restoring it with iTunes? Is it native to o2? If it is then restoring it shouldn't re-lock it. I believe it's only un-authorised unlocking that iTunes resets

 

Correct, if 02 unlocked it then its unlocked forever, no matter what you do with the phone.

Where as "un-authorised" unlocking can be un-done easily and sometimes accidently