The primary contact is the main person you deal with at each client.
The role of primary contact is important in Senta because generally each email and text message that is sent goes to the primary contact.
(That doesn't have to be the case -- you can set up client roles too, then you could nominate different contacts for payroll, tax, etc and they would receive relevant correspondence)
The first contact in the client's Contacts tab is always the primary contact.
Changing the primary contact
First, go to the Contacts tab, click Edit, then you'll see that each contact has up and down arrows and a rubbish bin icon, at the top right.
You can move contacts up and down using the arrow keys. If you move a contact to the top and he or she will become the primary contact. The previous primary contact will no longer be the primary contact.
The bin will delete the contact.
Click Save to store your changes.
Before you delete your primary contact, bear in mind that it might be useful to continue to see that contact's email messages -- it might be more suitable to just move them down instead, then you'll still see emails.