Function "letters_location_nearby_postalcodes_bylocation" missing

When the modules builds the array of zip codes, it calls the following function "letters_location_nearby_postalcodes_bylocation" which doesn't exist. Did I get a bad copy of the module?

I've also made numerous comments on drupalmodules.com. To clarify, I'm not trying to be a weasel or anything, but some additional functionality would be welcome as my client would love to have this working on their site.