We have an M300 base with two M25 phones. We have two different SIP servers configured, because in one we have better rates for outgoing calls but our historical number is used for incoming ones.
We found we can link two servers/extensions to a single handset, but we haven't figured out how to choose which service to use for outgoing calls.
How can we choose or set the default sip/extension for outgoing calls?
I think this might be what you are looking for: