Adding a custem text when declining a call

Hi

First of all my iPhone's 5 interface is not in english.

I'm trying to add a custem text when declining a call to the default 3 predefined text that are already there and i can't do it.

When reading some articles on the web, i should see in:

Settitngs/Phone/Calls/"Respond with text", at the bottom i shoud see a "What's up" sentence that when i tap on it i should be able to write what ever i want and it is saved for the next time i want to decline a call with the new text which i added.

The problem is that i don't see the "What's up" text, why ?

iany