Phone ansering service start up,need help asap

[Chad Toole]

I NEED HELP...i want to start a small answering service. Instead of using a switch board i want to just use mulit phones. But i want to answer the phone with the greeting for each business,so do i give each client a different number to forward their calls too? If i just use one number and different lines how will i know which client is calling?Confusing,...im sorry. please any advice will help