The simplest explanation, and therefore probably the correct one, is that you or someone else with physical access to your phone actually did send and/or receive 273 text messages that month.
...
Then explain why all of the texts counted on the bill were ones I wrote?
On top of that, to have access to my iPhone, I would have to be in a coma.
I wrote them all, I sent them all, and I received them all. The problem is if it is or is not charged as Text. It's an AT&T issue, not a what happened issue.