Free call indicator for iPhone users

David Pogue passes along a good tip for iPhone users on his blog:

You know, of course, that in general, cellphone calls to other people who have the same carrier as you (like Verizon or AT&T) are free, right?

But how do you KNOW when somebody with the same carrier calls you? How do you know it’s safe to yak all day without using up any minutes?

“In the iPhone address book, change the ‘mobile’ label for the caller’s contact info to ‘AT&T mobile,’ and that’s what will show up on your phone when she or he calls. Once you make this change for one contact, ‘AT&T mobile’ will show up as a custom label option for any contact.”

Link