How to activate my iphone 4s?

I just bought an unlocked iphone 4s and put my 3 network (uk) sim in it, it comes up with the message ' only compatible sim cards from a supported carrier may be used to activate iphon. Please insert sim that came with your iphone'! It has been factory reset by my mate so i dont have the original sim and when i plug it into itunes the device does not come up although my laptop recognises it with its audible tone! How do i activate it please?

You need the original sim, or call the carrier they might help.
if you need a factory unlocked already activated iphone 4s, email me i have a few for sale or trade

Http://www.three.co.uk/Support/Micro_SIM_upgrade
Simple from there:)

There's only one thing I will say to you. You should've got a Samsung.

Just unlock it