[Serusers] Caller ID How??

Hello, I have a question regarding caller ID currently I am catching some flak because when ou outbound calls ring to the PSTN they see ,for instance SER username is 6013, 6013 on their caller ID. How do you handle this to show a valid inbound number on a user by user basis. We have a couple different people that use our server for outbound termination only they want it for instance to show 888-555-1212. Is there anything I can do to force ser to show a fulle telephone number instead of a user. I was thinking of changing their username to be the phone number they want to show up but is their another way? Eric Haskins 978-375-6112 Cell