Can't change my address in iPhone Contacts app . . .

After many of tries on this subject, I found the trick. So if you try to change your address your iPhone will change it after saving but, revert back to the previous address you had stored. To fix this you must add a new address and then save it. After you add the new address close the app and open it back up (you should see the new address as well as the old one(s). Next just simply delete the old addresses and then you should be good.

Hope this helps!