How did you put them on the phone? What phone do you have?

 

Are they in your gmail account? Gmail has a duplicate contact utility for just such issues, and/or you can restore an earlier set of contacts, pre-duplicate.

 

You can try going to contacts settings, then go to contacts to display, then click custom, then click on the account listed there to expand options, you can check/uncheck the ones you dont want to see.