By Sam Oliver

Published: 10:00 AM EST

O2 began taking pre-orders for Apple's new iPhone 3G through its website early Monday but was forced halt the service just hours later as UK consumers flooded the carrier's servers and quickly consumed initial supplies.

O2's pre-order system falls flat

iPhone 3G hopefuls awoke Monday to emails and text messages from O2 announcing that they could pre-order their new Apple handset beginning at 8:00 a.m. local time this morning.

"If you want to place your order, all you need do is click on the link below on your Mac or PC, select the tariff, select the iPhone 3G model and sign a new 18-month contract online," the carrier said in its messages.

Successful pre-orders were to be delivered by a courier on launch day, Friday July 11th, and customers were to be able to complete activation through iTunes from their homes.

Minutes later, however, O2's automated upgrade system for existing iPhone owners buckled under pressure and was taken offline, leaving those customers without a means of placing their upgrade order.

At the same time, the pre-order system for new iPhone customers continued to function without a hitch, frustrating existing owners who were suddenly at a disadvantage given that O2 said it was taking pre-orders on a "first come, first served basis."

Faced with these issues, O2 hours later would shut down its pre-order system completely. A message on the carrier's website now informs customers that due to "huge demand," iPhone 3G is currently out of stock online. Customers are asked to check back for more information on Thursday, July 10th.

O2's iPhone 3G tariffs

The UK carrier has priced the 8GB iPhone 3G at £99 and the 16GB model at £159 with a £30 monthly tariff that includes 75 minutes, 125 text messages, and unlimited data.

A £35 tariff offers the handsets at identical prices and includes 600 minutes, 500 text messages and unlimited data.

Customers who step up to the £45 tariff get an 8GB iPhone at no cost, or a 16GB model for £59. The monthly plan includes 1200 minutes, 500 text messages and unlimited data.

Either iPhone 3G model is free with O2's £75 top-tier tariff that includes 3000 minutes, 500 text messages, and unlimited data each month. All tariffs require that customers agree to a new 18-month contract.



O2 also previously announced that iPhone 3G will also be available under its Pay & Go subscription model at £299.99 for the 8GB model and £359.99 for the 16GB model. Full details are available here, though it appears that O2 has delayed this offering until "later this year."