Returning a new value every time I call the method

I am trying to return a new value everytime I call this method, currently everytime it is called it keeps returning the same value:

public static int GenerateNumber()
    {
        Random randomNumber = new Random();            
        int number = randomNumber.Next(3, 19);
        return number;
    }

It is then called as such:

MeleeClass melee1 = new MeleeClass(GenerateNumber(), GenerateNumber(), GenerateNumber(), 50);

But when I run the code to see what is stored in the variables, they are all the same number. Thank you in advance for your help, sorry for any formatting mistakes it's my first time posting.