You have several options. First is to go back to the dentist who originally did the work and share your concerns.The second option is to get another opinion and move forward with a different dentist. Once you have committed to crowns your can't remove them without replacing them.
Unfortunately once you made a commitment to crowns by having the teeth prepared there is no way to reverse the decision. If the issue you are having is that you had gum recession which exposed the metal and root surface there are a couple options to look into. You could have the crowns redone with non-metal all ceramic crowns to prevent dark lines in the future. This would also cover over the newly exposed tooth due to the recession. The other option would be looking at gum tissue grafting to attempt to return the gum level to pre-crown levels although this may have less of a. Han e if working.