Converting Letters in Phone Numbers to Their Corresponding Digits

In a recent post, I mentioned that the feature that allows a user to tap on a phone number in their smartphone web browser and dial that number doesn't work if the phone number contains letters.  Well, some of the phone numbers in the database tables I'm working with contain letters (usually to spell out building abbreviations) so I needed to convert those letters into the corresponding digits on American phones (apparently it's not an international standard).

Before writing my own function to do this, I did some Googling and was a bit surprised to find that while folks have written routines in CFML to strip out dashes and such, no one had really written (and then published) a routine for this task.  So here's mine:

(Shrug) Nothing fancy, but it works. If you need to do additional adjustments to the phone number (like I did), you can just add them to this function or put them in separate functions (which is probably better).