Toll-by-plate, Destin FL, sent me a bill - WWtOTD?

We went vacationing in Destin at the end of May. Some new toll-by-plate system took a picture of my license plate and they've sent me a bill. It's not much, just $5.50 ($1.50 for each pass and a $2.50 administration fee). Apparently the admin fee can be avoided if you create a pre-paid account

They correctly have the dates listed that I both entered Destin and when I left.

Here's the thing, though. Both on the way in and the way out we physically stopped at a toll booth and paid a human being $3.00 cash.

I just asked the 3 other drivers if they received anything in the mail and they have not.

So, what the hell is going on here? Are there now 2 different tolls on the way in and out of Destin from I-10 or did they not record that I gave them cash at the toll booth?

Pay? Don't pay? Call the number on the paperwork and ask them WTF?

There isn't anything specific about the location where they're tolling me, it just says "Florida's Turnpike is transitioning to all-electronic tolling, which allows customers to pay tolls without slowing down or stopping as there are no traditional tollbooths."

When I Google'd Florida's Turnpike I got something from the Miami area.