Today is your day if you’re a Virgin Mobile subscriber. The carrier is now offering the iPhone 4 and the iPhone 4S with its prepaid no-contract plans that start at just $30 per month. You’ll need to drop a pretty penny for the devices, however. The iPhone 4 with 8GB of storage will set you back $549.99 and the 16GB iPhone 4S will cost you $649.99. Based on those prices, and considering that iOS 6 is coming this fall, we suggest you save the extra cash and buy the iPhone 4S so that you future-proof yourself just a bit. Virgin Mobile is offering the devices with an unlimited data and text plan with 300 minutes for just $30 per month, which is an incredible price considering you would pay about $70 more for those services on a larger carrier. A 1,200 minute plan costs just $10 more and an unlimited voice plan will set you back $50 per month. Virgin Mobile is also opening its first 10 retail stores to help bolster its sales, so if you live in the Chicago area you may want to visit one of the new establishments.