Virgin Mobile will be the next prepaid carrier to get iPhone. The carrier has confirmed rumors that it will carry iPhone 4 and iPhone 4S contract-free and the two Apple smartphones will go on sale June 29.

Virgin Mobile USA announced on Thursday that it will offer iPhone 4 and iPhone 4S to its prepaid customers, beginning June 29, with monthly contracts as low as $30. The disadvantage of discounted prices is that you have to pay a big upfront fee, just like in case of Cricket Wireless, which is the first carrier to offer iPhone without contract. The 8GB model of iPhone 4 is priced at $549, while you have to pay $649 to get iPhone 4S.

"This month marks Virgin Mobile USA's tenth birthday. And what better way to thank our fans for ten years of loyalty than by giving them exactly what they want: the perfect plan for the perfect phone. That is the essence of 'A Higher Calling'," said Virgin Group founder Sir Richard Branson.

The startup plan - $30 per month - gives you 300 minutes and unlimited text messaging, along with unlimited data. With the fair-use $40 per month plan, free calling minutes get increased to 1200. And the Everything Unlimited plan, costing $50 a month, gets you unlimited calling, messaging and data. Despite of being labeled as unlimited plan, it is not truly an unlimited data plan. After a user consumes 2.5GB of data in a month, the internet speeds will eventually slow down.

In case you want to use your prepaid iPhone as mobile hotspot, you have to pay additional $15 per month with the data cap increased to 3.5GB.

Cricket Wireless, a subsidiary of Leap Wireless, offers iPhone 4 for $399 and iPhone 4S for $499, which is considerably cheaper than Virgin Mobile's offering. However, you will get only one plan costing $55 a month that gives you unlimited calling, messaging and data, with data cap set at 2.3GB.