Prexar, USA Telephone’s mobile unit, has agreed to buy certain portions of Amp’d Mobile’s wireless assets and will take on Amp’d’s customers. Former Amp’d subscribers will likely be able to keep their phones and phone numbers, and can sign up for new services from Prexar through the company’s Web site. Prexar says that Amp’d subscribers should be able to transition their services seamlessly and without interruption. Prexar offers 4 different voice plans, ranging from $40 per month to $180 per month, and also offers messaging plans for additional charges. It offers three handsets of its own to new subscribers.