You could differentiate between the various contacts as separate jobs under the same customer. So you would have a customer, "Joe's Pizza" with different "jobs" that are actually the various contacts: Sam, Joe, Bob, etc.
If that sounds like it might work for you, here's a youtube video that will explain how: https://youtu.be/SdZNsWlps_Y
If you'd rather, here are the steps:
1. In customer center, right-click the customer that needs a new contact person
2. Click Add Job
3. For Job Name, enter the particular contact you wish to save
4. From here, you should be able to add the individual contact information you need.
5. Now, when you invoice, make a new SO/Estimate/etc., you will be able to input the customer either by typing the individual contact (e.g., Sam) or the customer (Joe's Pizza). If you enter the customer (Joe's Pizza), you will see the various contacts (aka Jobs) associated with that customer in the drop-down box: Joe's Pizza:Sam, Joe's Pizza:Joe, Joe's Pizza:Bob, etc.
Hope this helps.
