Unlocked Mobile Phones

An unlocked mobile phone is a mobile phone that is not under any network constraints so you can use it with any network's sim card. Buying an unlocked mobile phone is often called buying a phone "outright", which can be done from mobile phone stores or sometimes from networks themselves.

Advantages of Buying Unlocked Mobile Phones

• No lock-in contracts
• Can be used on any mobile network
• May be able to be used overseas
• Can be upgraded or downgraded at any time

Disadvantages of Buying Unlocked Mobile Phones

• Must be paid for in upfront in full
• Generally more expensive
• Contracts often come with "free" mobile phone
• No network warranties

If you have a mobile phone currently under contract, many networks will unlock the phone for you for a small fee. This will then allow you to use any other network sim cards in that mobile phone. Don't try and unlock the mobile phone yourself though, as this could result in your phone being "locked" by the network and ending up totaly nonfunctional.

Look here for a mobile phone on mobile phone plans.