CompetitorContactTrigger

trigger CompetitorContactTrigger on Contact (before insert, before update) {    
    
    //Get a list of all our Competitors' names from our Custom Metadata
    //Create an empty List of Strings to hold your Competitors' names
    for(){//Query your Custom Metadata and get its Label field
        //Add the Label to your List of Strings
    }
    
    //Create a Map of IDs to Accounts; populate your map on the same line by putting a query in the parentheses.
    //Your query will just get Account IDs from Account where the Name is in your List of Strings
    
    
    //Loop through your Contacts in Trigger.new
        //Check if your Map contains the AccountId from each Contact
            //If it does, set DoNotCall = true
        }
    }
}