Dental Works review: ruined my lower teeth crowns to make room for new crowns

Hello,
I went to Dental Works Royal Oak, Michigan, and got two crowns on my upper molars. Apparently they did the measurement of the crowns crowns, because they were too big and didn't fit. So, instead of ordering new ones, they worked on the crowns on the lower teeth to make room for the new ones, and I still feel the crowns weird in my mouth.
They thinned my existing crowns so much, that I am afraid they are gonna break. And the funny thing is that they told me I have to replace the old crowns because of a cavity under them.
Please advise.