Call diversion for multiple companies: know how to answer the phone

This solution is to forward calls to your mobile phone and know for which original number (company) someone is calling.
Let's assume that you own two companies: PizzaBakersInc and WebBuildersInc. When customers call you, you want to be able to answer with the name of the company they are calling for.
If your telephony provider can assign multiple addresses to you and your voip-router supports call forwarding such as my Fritz!Box does then this might be your solution.
First of all you need two telephone numbers:
12345 PizzaBakersInc
67890 WebBuildersInc
Place both numbers in your cell phone's address book with their company names.
Next you want to setup call forwarding to you mobile phone, see the examples of my Fritz!Box below.
The trick is that the outgoing called id must match the phone number you are forwarding. So for PizzaBakersInc you setup a call diversion for number 12345 to your cell phone and configure that the call going to your cell phone has 12345 as the caller id. By doing this when your phone rings the company name is displayed and you can anwer with the greeting: "Good afternoon, PizzaBakers, this is Rob, may I take your order please?" or "Good afternoon, WebBuilders, this is Rob, how can we improve your web site today?"
There are two disadvantages or things to watch out for:

• With call forwarding you are paying for these calls
• The phone number of the original caller is not displayed on your cell phone when receiving the call. You can however (if your routers supports it) find the numbers in the call log of your router.