New phone, very old sim. Help!

[FaverollesWithBoughsOfHolly]

I originally posted in chat, but this topic may be more appropriate :)

I've been given a samsung galaxy. My sim card is very old and doesn't work in it.
I haven't a clue what to do.
How do I keep my old number? If I get a new sim, does it automatically have a new number ( which would be fine)
I like the idea of giffgaff, but have no idea if it would work in my area (N Yorks)
I could really do with someone telling me exactly what to do! (in easy words )

Your SIM card should work but it sounds like the phone you have been given is locked to another network. Ask the person who gave it you, what network it worked on.

Giffgaff is great but it uses O2 network for its signal. So basically it will work anywhere you can get an O2 signal (ie. practically everywhere)

It had an orange 3G sim in it, that is/was my neices.
How do I unlock it?

Which model of Samsung is it?

Will Orange unlock it? That would be the easiest way. If not, there are tools out there for particular models of phone. Hence the question

If you get a new aim it will have a new number. HOWEVER if you ring up your network you can transfer your number across to the new sim. You just need to ring your network and ask for your PUK code. When you get it let your new network know and it transfers the number across. I did it from O2 to 3 when I got my iPhone. Easy todo and only took 2 days