Iphone 5 language changing problems?

When I set up my phone I did it in spanish, and I understand the language, but I changed it to english however some apps are still in spanish, how to i change them to english?

Added (1). The language setting IS English. My problem is that some apps (such as calendar) are still in Spanish. I tried changing it back to Spanish then English again, but that didn't work.

Just go to setting and you will find language changing setting