numery.rb

#!/usr/bin/env ruby

# I opted for a more conventional mapping, as in
# https://en.wikipedia.org/wiki/File:Telephone-keypad2.svg
MAP = {
  '2' => 'abc',
  '3' => 'def',
  '4' => 'ghi',
  '5' => 'jkl',
  '6' => 'mno',
  '7' => 'pqrs',
  '8' => 'tuv',
  '9' => 'wxyz'
}

number = gets.strip

raise "wrong format" unless number =~ /\d{9}/

lists = number.chars.map {|c| (MAP[c] || c).chars}

puts lists.shift.product(*lists).map(&:join)