This occurs periodically with various cell phone providers. Typically, the issue is that the message includes a "shortened URL" which opens the map web page showing the location of the message. Cell phone providers sometimes decide that ANY message containing a shortened URL is spam. Garmin beats them up and they stop blocking the messages. Until they don't.
The conventional wisdom is to disable this feature. In the lower right corner of the Account tab (your account at explore.garmin.com), there are several options for SMS Message Configuration. UNCHECK the box for "Include a link to an online map..." This removes the link from all SMS messages sent from devices on your account.
