Debugging Help...

[Fishsauce]

Any kind hearted person mine telling me what I'm screwing up?
This program is to convert letters into numbers, telephone style.

Error: the answer isn't coming up...
Warnings:
warning C4101: 'index' : unreferenced local variable

warning C4508: 'numberletter' : function should return a value; 'void' return type assumed

warning C4700: local variable 'len' used without having been initialized

warning C4715: 'check' : not all control paths return a value

Thanks
Fishsauce
Keep it simple please...I'm new to C++.

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

void main()
{
int check(string , int);
int numberletter(int , string, string);
int index;
string edited;
string letters;
string::size_type len;

cout << "Enter 7 numbers: ";
cin >> letters;
check(letters, len);
numberletter(len, letters, edited);
}

//************************************************** ****************
check(string letters, int len)
{

len = letters.length();
if (len == 7)
{
cout << endl;
cout << "You have entered correctly.\nLoading..." << endl;
cout << endl;
}
else
{
cout << "You have entered an invalid number.\nPlease enter 7 characters." << endl;
return 0;
}

}
//************************************************** ***************



numberletter(int index , string letters, string edited)
{
index = 0;
while(index == 7)
{
edited = letters.substr(index,1);
if (edited=="A" || edited=="B" || edited=="C")

cout << "1";

else if (edited=="D" || edited=="E" || edited=="F")

cout << "2";

else if (edited=="G" || edited=="H" || edited=="I")

cout << "3";

else if (edited=="J" || edited=="K" || edited=="L")

cout << "4";

else if (edited=="M" || edited=="N" || edited=="O")

cout << "5";

else if (edited=="P" || edited=="Q" || edited=="R")

cout << "6";

else if (edited=="S" || edited=="T" || edited=="U")

cout << "7";

else if (edited=="V" || edited=="W" || edited=="X")

cout << "8";

else if (edited=="Y" || edited=="Z")

cout << "9";

else

cout << "#";

index++;
}
}