Danny's right like usual.

Fax/Mail/Call all the usual clients about the number changes.

Until they get used to it, you can have the local Telco install "Closet jacks" at the old location (if they won't do it at the CO) for the main line and fax line with Call Forwarding on them engaged. Have these lines active for as long as your wallet stands it.

Ideally, you'll want to do this only short term, while clients get used to the new number.

Note: You don't need to leave your system on site at all...

Scientists say that the universe is made up of Protons, Neutron & Electrons. They forgot "Morons".
Dave. (CTUB) Canadian Techs Use Bix!