我的C++函数不断收到调试错误。我不确定我做错了什么

嗨，我对编程很陌生，对于这个程序，我应该能够使用函数计算某人的每月费用。当我编译它时，它很好，但是当我尝试调试时，它说我失败了，所以我无法判断我做错了什么。这是我的代码：

该程序计算用户的月费

#include <iostream>
#include <iomanip>
using namespace std;
//function prototypes
void showpackage();
void calculatePkg_A (int,int,int);
void calculatePkg_B (int,int,int);
void calculatePkg_C (int,int,int);

int main ()
{
    int inputPackage; //package choice
    double inputHours; //number of hours

    //constants for package choice
    const int pkg_A = '1' ,
               pkg_B = '2',
               pkg_C = '3';
     const char quit_choice = 'Q' || 'q';
    //constants for cost of package
    const int cost_A = 15,
              cost_B = 20,
              cost_C = 25;
    //constants for package access time
    const int hours_A = 50,
              hours_B = 100,
              hours_C = 150;
    cout << fixed << showpoint << setprecision (2);
    do
    { //display package options. 
        showpackage();
        cin >> inputPackage;
        //validate package selection
        while (inputPackage < pkg_A || inputPackage > pkg_C || inputPackage != quit_choice )
        {
            cout << "Please enter a valid package choice:";
            cin >> inputPackage;
        }
        //If user does not want to quit, proceed.
if (inputHours < 0 || inputHours > 720 || inputPackage != quit_choice)
        {
            //get the number of hours used
            cout << "How many hours were used?";
            cin >> inputHours;
                //display the total charges
                switch (inputPackage)
                {
                case pkg_A:
                    calculatePkg_A (cost_A, hours_A, inputHours);
                    break;
                case pkg_B:
                    calculatePkg_B (cost_B, hours_B, inputHours);
                    break;
                case pkg_C:
                    calculatePkg_C (cost_C, hours_C, inputHours);
                    break;
                }
            }
    } while (inputPackage != quit_choice);

            return 0;
}

//definition of function showPackage which displays package options
void showPackage()
{cout <<"An Internet service provider has three different packages for its customers: n"
<<"1.Package A: For $15 per month with 50 Hours of access provided, additional hours n"
<<"are $2.00 per hour over 50 hours.n"
<<"2.Package B: For $20 per month with 100 Hours of access provided, additional hours n"
<<"are $1.50 per hour over 100 hours.n"
<<"3.Package C: For $25 per month with 150 Hours of access provided, additional hours n"
<<"are $1.00 per hour over 150 hours.n"
<<"Enter your choice either 1,2, or 3:";
}
//defintion of function calculatePkg_A. Displays total charges.

void calculatePkg_A (int cost_A, int hours_A, int inputHours)
    {
        cout << "The total charges are $"
             << (cost_A += (inputHours - hours_A) * 2) << endl;
}
//
//defintion of function calculatePkg_B. Displays total charges.
//
void calculatePkg_B (int cost_B, int hours_B, int inputHours)
    {
        cout << "The total charges are $"
             << (cost_B += (inputHours - hours_B) * 1.5) << endl;
}
//defintion of function calculatePkg_C. Displays total charges.

void calculatePkg_C (int cost_C, int hours_C, int inputHours)
    {
        cout << "The total charges are $"
             << (cost_C += (inputHours - hours_C)) << endl;
}

但是每当我尝试调试它时，我都会收到错误消息：

1>Program5.obj : error LNK2019: unresolved external symbol "void __cdecl calculatePkg_C(double,double,double)" (?calculatePkg_C@@YAXNNN@Z) referenced in function _main
1>Program5.obj : error LNK2019: unresolved external symbol "void __cdecl showpackage(void)" (?showpackage@@YAXXZ) referenced in function _main
    1>C:UserscharlotteDesktopprogram5Debugprogram5.exe : fatal error LNK1120: 2 unresolved externals