Why don't my Emojis work.iPhone 4 iOS 6.0.1 iMessage?

People get my Emojis but I don't get theirs I get?=? Sometimes I get blanks. Btw everything is updated on my phone and my emoji keyboard is on. Is there an emoji app I should download if yes please give me the link. And iMessage doesn't always work with all iPhone users its set as text message instead of iMessage" and they get my Emojis even when I use text message but I don't get their. If you have an answer thank you: D

Https://itunes.apple.com/us/app/emoji-2-emoticons-free-±photo/id444304133?mt=8