tonyhughes: get the ESN number (decimal or hexadecimal). call *123 or  a dealer. Ask if the phone is "free on the network" and able to be connected.

The funny thing is some 123/6 CSR's do not know what a hex esn is, and tell customers that’s not an esn, and send them to the dealer!!

If you wish to wish to action the esn change (if the esn is free); then all u need to do is call 123 OR visit your local Telecom Dealer. Just do not try to bypass 123 by calling a dealer and asking for an ESN change or swap. Over the phone request should be completed via the 123/6 help desk, as they will be able to identify postpaid customers. Prepaid esn changes can also be actioned via the Prepaid Help Desk on 0800 32 32 32. Telecom Dealers should action this for you in person, and not over the phone.

Best of luck with your search for a new handset. The process is easy, just make sure the esn is free, and or if connected to prepaid no passwords or bars (lost/stolen) have been placed on the handset's esn / current mobile number.