Verizon

Verizon, the largest carrier in the U.S., has admitted today that a network glitch is preventing some smartphone/tablet users from accessing the 4G LTEnetwork.

Says the company: 

Customers are temporarily unable to activate any 4G LTE devices.

Users can still use their phones on 3G and make voice calls, but Verizon says they are working to restore LTE to all affected customers. 

The carrier says it will restore the service market-by-market

To date, Verizon has sold over 500,000 4G devices, most of which are HTC Thunderbolts.