Repeated seeded random number in c++

I am trying to get the random number (x) to get different result. Every time I run the program, I am given the same number, in result the same response. I am making a magic 8 ball. I am curious whether the srand or the rand is used wrong because I have tried messing around the

x= rand() % 16+1

Here is my code at the moment.

#include <iostream>
#include <iomanip>
#include <cstdlib>  
#include <ctime>       
using namespace std;

int main() 
{
   int x, y;    
  // do
   {
    cout << "Ask me a question. (Entering 20 will leave the program!)\n";
    cin >> y;
    if (y == 20 )
    srand (time(NULL));
    x = rand() % 16 + 1;
    switch (x)
    {
        case 1:
            cout << "Ask again\n";
            break;
        case 2:
            cout << "Question too vague.\n";
            break;
        case 3:
            cout << "Don't count on it.\n";
            break;      
        case 4:
            cout << "Yes.\n";
            break;
        case 5:
            cout << "As I see it, yes.\n";
            break;
        case 6:
            cout << "My reply is no.\n";
            break;
        case 7:
            cout << "Cannot predict now.\n";
            break;
        case 8:
            cout << "Outlook good.\n";
            break;
        case 9:
            cout << "You may rely it.\n";
            break;
        case 10:
            cout << "You will have to wait.\n";
            break;
        case 11:
            cout << "Sure, why not?\n";
            break;
        case 12:
            cout << "Go for it!\n";
            break;
        case 13:
            cout << "Very doubtful.\n";
            break;
        case 14:
            cout << "Concetrate and ask again.\n";
            break;
        case 15:
            cout << "Who knows.\n";
            break;
        case 16:    
            cout << "The world may never know.\n";
            break;
    }
   }        
}