Registered SIP '702' at xx.xxx.xx.xx port 33124 expires 120

Any ideas? I have a client with a remote phone. I am watching CLI and I see this message pop up on this extension. It seems to always register to a different port other than 5060 and there seems to be no reason that I can see. The client is connected via a Linksys Router -> Cable Modem -> to office / Trixbox - not using VPN at the moment. If I take the router out of the picture I have had mixed results. For a week without the router it seemed to register to 5060 and stay online. I have factory reset the router and still get the same results. I am ready to swap the phone and/or the router? BTW - the client has an Aastra 6757i CT.

Thanks!