You can revoke the permissions from those you want to stop sharing data with, simply by following these steps:
1. From Salestrail app:
Open Salestrail app > Permissions > Permissions > Revoke Permission.
2. From the Dashboard:
Go to the Dashboard > Team > Revoke.
After that, you should see the invitation from the person whose permission has been just been revoked. You can grant the data-sharing permission in the future if you want to.
If you know you'll not share your call data with this person ever again, you can discard the invitation by clicking on the "x".