A new snapshot is available which should resolve the outgoing caller id issues with pb13. Incoming caller id can now also be prepended or replaced with a user defined string. Finally, SIP phone accounts have "nat=yes" set by default. There was a consensus that this is a more logical default. Please report if it breaks previously working phones (do give them enough time to reregister).
http://downloads.askozia.com/pbx/snapshots/r420Enjoy!