I noticed this in Garmin's last postmortem on the AT&T issue of late:
"After several attempts to get the issue corrected both through communication with our SMS partner and software changes, we have chosen to revert to using long URLs in text messages.
This has the unfortunate consequence that many text messages will now span more than one message, adding to the volume of messages the recipient receives on their phone. It also affects customers of all carriers, not just AT&T."
I reported on this a year ago, when I received four messages, from one text that was sent to me. And the character count was far less than what may be attributed to hidden required back-end info. Since Garmin seems to be unable to make headway in this challenge with all of their carrier "partners", they should give a larger allowance to messages on each plan, since this is different than the marketing of the plans. It's clearly not just an AT&T thing. Just sayin.