actually as you dial you will see the letters showing up as a search. Directly under that you will the numbers appearing. Just put the number in and press send (green button)
In OS 5.0 you hold down the Alt key if the letter coincides with a number key and it puts it in as a letter. You have to kinda switch back & forth using the Alt key. Start with the number '1' then put in the letters & numbers. when you are done, scroll back and remove the '1' then press dial. Post back if this works for OS 6.0 also.
For dialing numbers that have letters, such as 1800VERIZON (just an example, not a real number), all you have to do is first press the green talk button and then dial the number. When you reach where the letter is supposed to appear, hold down the alt button and the letter will appear in the string. Hope this helps.