c++程序不会退出while循环

当用户输入'Q'或'Q'退出程序时，我的c++程序不会退出下面的while循环。前两个选项工作得很好，并调用相应的函数，但'Quit The program'选项只是无限期地重新开始while循环。

#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
int main()
{
    char choice; //Varible to hold the user's choice.
    while (choice != 'Q' || choice != 'q')
    {
        //Display the menu and retrieve the user's choice.
        cout << "Please choose from one of the options below:nn";
        cout << "A. Calculate the total amount of your bill [Enter A]n";
        cout << "B. Calculate your BMI [ENTER B]n";
        cout << "Q. Quit the program [Enter Q]nn";
        cout << "Enter your choice: ";
        cin >> choice;
        //Either calculate the user's bill or their BMI based on their choice.
        if (choice == 'A' || choice == 'a')
        {
            caLculateBillAmount();
        }
        else if (choice == 'B' || choice == 'b')
        {
            calculateBMI();
        }
    }
    return 0;
}