When phone is new this condition doesn't happen.
I have two vodafone sim.
The first is mine and i use it on my 8390 since i bought it.
The second one has never been inserted on the 8390.
With the 1st i get the no service after 2-3 hours.
With the 2nd i never get the no service.
If I observe to them I notice that the 1st it is bended!
Yes! The 8390 bends the sim! If u remove the battery you'll see that the contacts makes too much pressure on the chip!
I inserted the 1st sim in a Nokia (bleah :-& ), it haves a better way to handle the sim and it has straightened it.
For now i don't get no more "no service" messages...
Someone must find the solution