[lmkg]

This is what the average phone bad looks like in the United States:

http://www.pachd.com/free-images/technology-images/phone-dia...

There is a standard, universal mapping of letters onto numbers. This allows companies to advertise their phone number as something memorable like 1-800-CASH-4-AU and everyone knows how to dial it. People don't even need to remember the mapping of letters, because they're printed on every keypad.