Question

So it seems everything I do with Regex doesn’t do what I expect it to do. This statement, I expect to toss out any letters and require 3 digits at minimum and most, but it doesn’t require 3 digits. It indeed disallows letters but any number of digits is good.

myReg = new Regex(@"(^[a-z])([0-9]{3,3})*");

I expect the ^[a-z] to toss out letters and the [0-9]{3,3} to require 3 digits.

Might as well add the whole code block, wasn’t thinking.

userData = phone.Text;

myReg = new Regex(@"(^[a-z])([0-9]{3})+");

        foreach (var validName in myReg.Matches(userData))
        {
            if (myReg.IsMatch(userData))
            {
                phone.Clear();
                badData.Visible = true;
                phone.Focus();
            }
        }

Answer 1

That matches

One character that isn't a letter from a to f, stored in a backreference,
followed by zero or more instances of: 
    3 characters that are digits from 0-9
    stored in another backreference.

I think you need: ^[0-9]{3}+$

This matches a string that contains:

One or more instances of:
    3 characters that are digits from 0-9

If you instead simply need a string that consists of more than 3 characters and entirely of digits, you can use:^[0-9]+$