jims:

1. Try to replicate problem when you are there by having someone dial out from that phone.
2. Try to determine if it is the phone (port) or a line. Do other phones have the same problem? Is it just one line or ALL the lines.
3. What kind of service do you have coming in? Just regular POTS or do you have a T-1 with a channel bank?
4. Sounds like a syncro problem with the carrier--but do some basic troubleshooting before calling them.
5. Are you sure it isn't a cell phone that is being use at the other end?
Good luck.