A little help

I'm trying to figure out how to code a program where it prompts the user to enter seven letters of a phone number than the output is the numbers of those letters like on a telephone. I always get 999-9999 though. I'm a beginner too so that's why I'm not too great at it yet.

EDIT: Well, this is what I have no though I've probably made it more complicated than it should be being that it's my first project. The farthest I've gotten is my class is to the end of while loops or something I think well...this is #include
using namespace std;
int main() {
int num1=0, num2=0, num3=0, num4=0, num5=0, num6=0, num7=0;
char letter[7];
if (letter[1] == 'a', 'b', 'c')
num1 = 2;
else if (letter[1] == 'd', 'e', 'f')
num1 = 3;
else if (letter[1] == 'g', 'h', 'i')
num1 = 4;
else if (letter[1] == 'j', 'k', 'l')
num1 = 5;
else if (letter[1] == 'm', 'n', 'o')
num1 = 6;
else if (letter[1] == 'p', 'q', 'r', 's')
num1 = 7;
else if (letter[1] == 't', 'u', 'v')
num1 = 8;
else if (letter[1] == 'w', 'x', 'y', 'z')
num1 = 9;
if (letter[2] == 'a', 'b', 'c')
num2 = 2;
else if (letter[2] == 'd', 'e', 'f')
num2 = 3;
else if (letter[2] == 'g', 'h', 'i')
num2 = 4;
else if (letter[2] == 'j', 'k', 'l')
num2 = 5;
else if (letter[2] == 'm', 'n', 'o')
num2 = 6;
else if (letter[2] == 'p', 'q', 'r', 's')
num2 = 7;
else if (letter[2] == 't', 'u', 'v')
num2 = 8;
else if (letter[2] == 'w', 'x', 'y', 'z')
num2 = 9;
if (letter[3] == 'a', 'b', 'c')
num3 = 2;
else if (letter[3] == 'd', 'e', 'f')
num3 = 3;
else if (letter[3] == 'g', 'h', 'i')
num3 = 4;
else if (letter[3] == 'j', 'k', 'l')
num3 = 5;
else if (letter[3] == 'm', 'n', 'o')
num3 = 6;
else if (letter[3] == 'p', 'q', 'r', 's')
num3 = 7;
else if (letter[3] == 't', 'u', 'v')
num3 = 8;
else if (letter[3] == 'w', 'x', 'y', 'z')
num3 = 9;
if (letter[4] == 'a', 'b', 'c')
num4 = 2;
else if (letter[4] == 'd', 'e', 'f')
num4 = 3;
else if (letter[4] == 'g', 'h', 'i')
num4 = 4;
else if (letter[4] == 'j', 'k', 'l')
num4 = 5;
else if (letter[4] == 'm', 'n', 'o')
num4 = 6;
else if (letter[4] == 'p', 'q', 'r', 's')
num4 = 7;
else if (letter[4] == 't', 'u', 'v')
num4 = 8;
else if (letter[4] == 'w', 'x', 'y', 'z')
num4 = 9;
if (letter[5] == 'a', 'b', 'c')
num5 = 2;
else if (letter[5] == 'd', 'e', 'f')
num5 = 3;
else if (letter[5] == 'g', 'h', 'i')
num5 = 4;
else if (letter[5] == 'j', 'k', 'l')
num5 = 5;
else if (letter[5] == 'm', 'n', 'o')
num5 = 6;
else if (letter[5] == 'p', 'q', 'r', 's')
num5 = 7;
else if (letter[5] == 't', 'u', 'v')
num5 = 8;
else if (letter[5] == 'w', 'x', 'y', 'z')
num5 = 9;
if (letter[6] == 'a', 'b', 'c')
num6 = 2;
else if (letter[6] == 'd', 'e', 'f')
num6 = 3;
else if (letter[6] == 'g', 'h', 'i')
num6 = 4;
else if (letter[6] == 'j', 'k', 'l')
num6 = 5;
else if (letter[6] == 'm', 'n', 'o')
num6 = 6;
else if (letter[6] == 'p', 'q', 'r', 's')
num6 = 7;
else if (letter[6] == 't', 'u', 'v')
num6 = 8;
else if (letter[6] == 'w', 'x', 'y', 'z')
num6 = 9;
if (letter[7] == 'a', 'b', 'c')
num7 = 2;
else if (letter[7] == 'd', 'e', 'f')
num7 = 3;
else if (letter[7] == 'g', 'h', 'i')
num7 = 4;
else if (letter[7] == 'j', 'k', 'l')
num7 = 5;
else if (letter[7] == 'm', 'n', 'o')
num7 = 6;
else if (letter[7] == 'p', 'q', 'r', 's')
num7 = 7;
else if (letter[7] == 't', 'u', 'v')
num7 = 8;
else if (letter[7] == 'w', 'x', 'y', 'z')
num7 = 9;
cout << num1 << num2 << num3 << "-" << num4 << num5 << num6 << num7 << endl;
return 0;
}
I just gotta figure out what's going wrogn now its givin me 222-2222 now. I really apologize to anyone whos getting frustrated with me or anything. Thanks to all that help, I just gotta figure out what to do since I'm probably only supposed to use the knowledge I've already read through.