If that is the case, you will need a contact list in SharePoint PER sales person. Each user can only see their own contacts, but there will be a group of other managers who can see everyone’s contacts. Let’s say that the business tells you that in SharePoint, the contact lists need to be restricted.
The main driver here is who can see the contact records. In this case, the business came to you and said “we need to store out contact lists from our sales team in SharePoint”. Hopefully before you configure anything in SharePoint, you have a need or requirement. First thing we need to do is determine how many lists we will need, and that will depend on our requirement. Since SharePoint is the repository we want to use to primarily store our contacts, we need to create a list or lists to store them.
The great news is that you don't have to open the SharePoint interface just to add or update a contact.