Re: HELP! What phone service to use.
Typically, the client would pay for an 800 number service and have his phone line transferred to the 800 number, which in turn is transferred to you. When you see that 800 number on your caller ID, you know it is for that specific client. You can also set up a voice mail in case you are unable to answer the calls and it will have that client's branding. Freedom Voice, OneBox, Ring Central are just a few that offer the 800 numbers. You could also go the VOIP phone way and use Vonage (an example only). You'll need to compare costs to see which is more feasible for the client.