Issue
If you try to delete contacts in your Segment, it'll only give you the option to delete the segment itself and not the contacts. However, if you try to delete a list, it will allow you to delete the list or the list and the contacts all together.
Product
Twilio SendGrid Email
Resolution
1. Click on your Segment and hit the button "Export CSV"
2. Upload the exported CSV file related to the Segment and choose this option "Add Contacts to a new list" name it with an obvious name, something like "contacts to delete" so you can be sure you are deleting ONLY the contacts you need
3. Check the email notification sent from SendGrid with subject "We've Finished Processing Your SendGrid Contact Upload!"* to confirm if all contacts were uploaded as expected
4. Then, if all contacts were uploaded successfully delete the list, choosing the following option "Delete this list and permanently delete all xxx contacts associated with this list from my account". This will allow you to delete the list and the contacts associated with it
Additional Information
*The email notification about Contact/Segment exports will go to the admin email on file (based on the login accessing the account) or the email address listed under "Marketing > Notifications".