O2, one of the carriers of the iPhone in the United Kingdom, announced today that they will begin capping data usage.

New customers and those upgrading to the new iPhone 4 on or after June 24th will have to choose a new data plan that has data caps ranging from 500MBs to 1GB.

O2 said they will be sending out text messages to customers on limited data plans to let them know when they are getting close to the cap.

It will be interesting to see if other carriers also follow suit, or if this move will affect O2's sales of the iPhone 4.

Of course, this news doesn't come as a shock to iPhone users in the United States, as AT&T recently announced that they will begin capping data on new iPhone users.

Also of interest is that TUAW notes that there are now five carriers that those in the UK can choose for their iPhone 4, including Three, which signed on today to offer pre-orders of the iPhone beginning June 15th. Needless to say, the competition will be high in the UK.

You can read more information on O2's data capping on their website.