Is my iphone 4s unlocked to all networks? - 1

When i go into Settings > carrier and turn automatic off, i get a screen with a list of networks, eg o2 uk, vodafone uk, three uk, orange. Currently i have a vodafone sim card in the iphone on pay as you go, but i need to change it to a three sim card on contract.
By the way i'm running ios 6.1 if thats any help

Well since you are paying pay as you go currently. That means your phone is unlocked because if it wasn't, chances are you wouldn't be able to have the pay as you go option.
What's good about having your phone unlocked is that you can go to any companies.
And because almost all of the companies have iPhones as part of their phone choices, you'd be able to have your iPhone still unlocked, still pay as you go, with a different company.

PAYG phones can absolutely be locked. Please do not listen to that advice.

To check if the phone is locked or not, simply insert a SIM card from any other than Vodafone and check to see if it can receive a phone call. If it can, then the phone is unlocked.

Try this with two different SIM cards if the first doesn't work, just to be sure. You don't want to purchase an unlock if you don't need to!

If you need an alternative SIM card, simply order one from the network companies. They'll send you them for free and you won't have to top them up to test receiving a phone call.

If you can put in a SIM other than your original and it works, it is unlocked. The only other way to tell is to pay a service to do a carrier/unlock status check, this would officially give you an answer