When someone leaves the company you need to do 2 things.
1- You can either delete the person that is leaving or you can edit his/her profile if you know who is going to replace him/her. Please visit the support article on how to add / edit / remove a Ringio user.
2- If the person had a CRM profile (either ZOHO or Salesforce) you need to delete that as well.
Click on Other Apps and then click on PhoneBridge
Click on the "Add phone number" button and add the phone number of the person that is leaving with a 1 in front (total of 11 numbers). If it is a Personal Number then only one person will be under the phone number. If it is a company number then more than one person may be under the phone number.
Click on the "Associate user" button and then click on the minus sign next to the person that you want to remove.
You also may want to delete the person from ZOHO itself by going again to setup but this time clicking on "Users".
Since you have removed the person from Ringio in step 1, the person's calls will not be synced with Ringio anymore. You may want to remove the person from Salesforce itself by clicking on setup and then going to the Manage users link on the left column.