Open margins on crowns. Cold sensitivity. 4 teeth done at once. I do not trust this dentist. Went elsewhere.

New dentist saw open margins. Dentist who placed crowns disagrees, replaced only one. Cold sensitivity lessesed but is not gone. I complained to insurance company. His office now says to come back. Crown done twice has a spot where my fingernail fits into it. It's still not right. What do I do? One of the crowns is bothering me more now than it was. I need guidance. I have medicaid, so it was covered, but it seems I have no choice and have to go back to him. Please advise ASAP. Thank you.