How to change from numbers to letters when making a call on IPhone 4?

How to change from numbers to letters when making a call on IPhone 4? - 1

You don't "change" from numbers to letters, silly. If you are given a phone number that contains letters, you simply press the number key that has that letter on it. For example, if you need the letter J, you press the 5 key. The letters are just representations of numbers. There are only numbers in a phone number.

You don't. The letters you may see used for some phone numbers are on the keypad already. Just dial the number with the letter you need on it. Like the old 1-800-CALL-ATT was 1-800-2255-288