They will refrain from nothing in order to deny your claim. Mostly they will try to prove that your condition was pre-existing, or that you haven't provided them with sufficient info to process the claim.
If you ever sign an authorization to release info with them, make sure you write the claim number on the page - their claim document is a 2 page one, the 2nd page contains only your signature and there is NO mentioning of the claim number anywhere (borderline illegal practice). They tried using this trick with my dr and almost managed to jeopardize my relationship with her.
I'd stay away from them