Changing networks - do I need a new SIM

This is probably a very basic question, but here goes: If I have a
T-Mobile SIM and use T-Mobile, but want to move to Virgin, do I have to
get a Virgin SIM and then port my T-Mobile number to the Virgin SIM, or
is it possible to change networks without changing SIM?

Thanks for any info

"SpongePaul" <paul.rubens@lineone.net> wrote in message
news:1147544417.093049.323810@i40g2000cwc.googlegr oups.com...
> This is probably a very basic question, but here goes: If I have a
> T-Mobile SIM and use T-Mobile, but want to move to Virgin, do I have to
> get a Virgin SIM and then port my T-Mobile number to the Virgin SIM, or
> is it possible to change networks without changing SIM?
>
> Thanks for any info

No you need a new SIM and you need to ring your present network for PAC
number which will allow you to transfer across.

Tim
>