Converts a alphanumeric phone number to its numeric equivalent. A typical phone dialpad has each number mapped to 0, 3 or 4 alphabet letters

The internationally standard phone dialpad has each number mapped to 3 or 4 English alphabet letters. The letters are used to create an memorable phone number like 1-800-Flowers, which is used on both mobile and landline telephones. The number 1 is usually used to retrieve a voice mail.