Remove Duplicates

I have a report that I am working on that shows active Projects on Hurricane Evacuation routes. I use a slicer containing all the districts and counties. There are 3 tables connected to the slicer, 1. Contract and Project Information, 2. Agency Personnel Contact Information, and 3. Emergency Contact Information for each Contractor. At first when there is nothing specified in the slicer, the Emergency Contractor Contact Information has duplicates; not because there are duplicates in the database, but because one contractor can be assigned to multiple contracts/projects (this is essentially the same thing happening with the Agency Contact Information table because multiple districts and counties are assigned to one Engineer). Is there a way to remove the duplicates in one or more tables before the criteria in the slicer is selected? Then after that if a contractor is assigned to multiple projects in different districts, I am fine with it showing duplicates at that point. Apologies if this is a confusing question, but I have tried all I know to fix this issue.