I have an installation with three sites, connected via VPN, each with a UC-520 and using SIP service. The headquarters handles all incoming calls and the desire is for the other two sites to have the HQ's phone number displayed as the outbound caller id. The service provider cannot do this since the desired number is not within the account of the two remote offices. They have suggested that the UC-520 be configured to report the outbound caller id for these two sites.
I have searched but could not find information to indicate if this is possible or reference info on how to configure this.
Any assistance would be most appreciated.