Snom 320 auto config picking up correct extension

[synaxis]

I have site to site VPN between Office and remote location

Took my snom 320 on holiday to remote location, plugged in the phone picked up my extension (13) and just worked

Brought the phone back to the office, plugged it in, now it auto configs to a different extension (19)

How do I make it go back to the original extension?

[AramK]

I can just guess, that from remote location the Quadro's WAN IP is visible only and you've configured your phone as a remote extension before, that's why you phone worked. When you moved to Office and plugged the phone, it got configured by P-n-P on first free extension, which was ext.19. Just check the IP-Line configuration for ext.13 and make it Inactive if there is configured some phone, that is not your Snom320. Make Inactive the IP-Line of ext.19 too. Then try to configure your Snom320 again.