CanI buy a PAYG SIM card for my old hand set? ( I have no clue about mobiles)

[headintheclouds]

I'm embarrassed that I'm such a dinosaur about anything remotely technical, BUT....
I'm about get an upgrade from an HTC desire to an I phone with vodaphone . Will I be able to buy a SIM card for the 'old' handset and give it to my DS ?

I'm assuming when the iPhone comes Ill have to transfer the sim from the HTC to the iPhone. So is there a way to give the handset to my little darling without having to unlock etc.. I know all you computer geeks out there will be thinking I'm soo ignorant but can you please help.

Yes, you can get a PAYG sim and stick it in the old phone. And yes, you will need to put your sim in the iPhone. Just make sure all your contacts are on the sim before wiping them from the phone.

The old handset is probably locked to Vodafone, so you may not be able to put any old SIM in it. If you ask Vodafone nicely they may unlock it for you. They may ask you to pay to unlock it, but if it's more than a tenner it can probably be unlocked at your local mobile store/market for less.

If it is not unlocked, it will have to be a Vodafone SIM that you put in.