I also live in Houston and that does sound like too much!
I put in the zip code for our Texas Medical Center into Healthcare Bluebook—and came up with a ballpark figure for a spinal MRI of $648 (with contrast added):
There wasn’t a specific estimate for a neck MRI, except if it was angiography, but came up with a $610 ballpark figure for that test:
Even with extenuating circumstances, it’s hard to imagine how this could be $15,000 for just 2 MRIs?
Check the details of your MRIs, and you can not only pull up estimates from Healthcare Bluebook, but also Fair Health Costs, Guroo (and there seem to be more and more websites every day)! Then take this information to the business manager of your provider and ask (politely) why their costs are so much higher?
If you run out of time to pursue this, feel free to any of the patient advocates on Nerdwallet or Advoconnection—and if you have any other questions, I can always try to help you figure out why one of our hometown groups is charging you so much!