We were asked last week if we (SingleOps) had a phonebook...
We do! Or... rather... YOU do!
You can use SingleOps' global search filter to enter either a client name, company name, or a partial phone number (if you know it).
If the number resides within your client database, it will be found and the client or company name returned to you in the global search results. NOTE: you may need to drill into the client record to actually see the phone number.
But remember... YOUR phonebook is only as good as YOUR data entry. ☺ So the next time you're doing an estimate onsite and you're tempted to hastily create a customer/client record by entering only the name and saving... you do so to your own detriment.
See also: Optimal Searching, Sorting, and Filtering