Hi Chris,
Here are a couple of things you can try:
1) Navigate to Customize > Tables / Fields, locate the Activity table and select Edit Table… Verify that the Automatic Reminders data looks correct.
2) If you don’t use this template on the backend of any of your screens, make a copy and delete the original. Maybe you re-used an activity template for this email template and since the activity screen is linked, it’s sending this template as an email.
If you are still unable to resolve this, give out support number a call at 1-888-925-6238 x2. One of our support team members will be able to investigate further.
I hope this helps.
-Audisho