Help Using Switch to Switch a Letter to a Number in a Function

[EaglesFan91]

I'm new here and am just looking for some help. It would be greatly appreciated if someone could give me hint to help me with my project for simulating dialing a phone number. the part I need help on is the toDigit() function. In the toDigit() function I have to pass the variables by reference and if the its a letter that was inputted, lowercase has to be made to upper case and if the digit is valid return 0 or if the digit is invalid return -1. thanks for any help or hints!

#include <iostream>
#include <iomanip>
#include <string>
#include <cctype>
using namespace std;

//Function prototypes
int readDials(char &d1, char &d2, char &d3, char &d4, char &d5, char &d6, char &d7, char &d8);
char toDigit(char &d1, char &d2, char &d3, char &d5, char &d6, char &d7, char &d8);
void acknowledgeCall(char &d1, char &d2, char &d3, char &d4, char &d5, char &d6, char &d7, char &d8);

char d;
int returnValue = 0;
int main()
{
while (returnValue != -5)
{
char d1 = ' ', d2 = ' ', d3 = ' ', d4 = ' ', d5 = ' ', d6 = ' ', d7 = ' ', d8 = ' ';
readDials(d1, d2, d3, d4, d5, d6, d7, d8);

if (returnValue == -1)
{
cout << "ERROR - An invalid character was entered\n" << endl; continue;
}
else if (returnValue == -2)
{
cout << "ERROR - Phone number cannot begin with 0\n" << endl; continue;
}
else if (returnValue == -3)
{
cout << "ERROR - Phone number cannot begin with 555\n" << endl; continue;
}
else if (returnValue == -4)
{
cout << "ERROR - Hyphen is not in the correct position\n" << endl; continue;
}
else if (returnValue == -5)
{
returnValue = -5;
}
else
{
acknowledgeCall(d1, d2, d3, d4, d5, d6, d7, d8);
}
}
system("pause");
}

int readDials(char &d1, char &d2, char &d3, char &d4, char &d5, char &d6, char &d7, char &d8)
{
cout << "Enter a phone number(Q to quit): ";
cin >> d1;
if (d1 == 'Q' || d1 == 'q')
{
returnValue = -5;
return returnValue;
}
cin >> d2 >> d3 >> d4 >> d5 >> d6 >> d7 >> d8;

toDigit(d1, d2, d3, d5, d6, d7, d8);

if (returnValue == -1)
{
returnValue = -1;
return returnValue;
}
if (d1 == '0')
{
returnValue = -2;
return returnValue;
}
if (d4 != '-')
{
returnValue = -4;
return returnValue;
}
if (d1 == '5' && d2 == '5' && d3 == '5')
{
returnValue = -3;
return returnValue;
}

return 0;
}

char toDigit(char &d1, char &d2, char &d3, char &d5, char &d6, char &d7, char &d8)
{
toupper(d);

switch (d)
{
case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': returnValue = 0; break;
case 'A': case 'B': case 'C': d = 2; break;
case 'D': case 'E': case 'F': d = 3; break;
case 'G': case 'H': case 'I': d = 4; break;
case 'J': case 'K': case 'L': d = 5; break;
case 'M': case 'N': case 'O': d = 6; break;
case 'P': case 'Q': case 'R': case 'S': d = 7; break;
case 'T': case 'U': case 'V': d = 8; break;
case 'W': case 'X': case 'Y': case 'Z': d = 9; break;
default: returnValue = -1;
}
return 0;
}

void acknowledgeCall(char &d1, char &d2, char &d3, char &d4, char &d5, char &d6, char &d7, char &d8)
{
cout << "Phone Number Dialed: " << d1 << d2 << d3 << d4 << d5 << d6 << d7 << d8 << "\n" << endl;
}


When I input letters as the number the end results show the same letters I entered. For example if I enter: abc-devg, it will say the number dialed is: abc-devg.

[EaglesFan91]

I have figured out the problem!