Why can I not always receive iMessages on my iPhone?

After I updated my iPhone to ios 7 I'm not receiving iMessages until I get back home or put 3G on. Before messages would automatically turn to sms text messages if one person doesn't have Wi-Fi. This means I'm not receiving important messages until I get back home and it is too late. And my phone also doesn't receive pictures unless I put 3G on. So if I randomly put 3G on I get pictures from months ago. Does anyone know how to fix this?

Added (1). I already have iMessage and SMS checked off in my settings and it still isn't working.

Added (2). If you don't understand the question please don't be rude and say I don't know what I'm talking about. IMessage needs Wi-Fi.

Go to Settings > Messages
Check the settings for SMS and iMessage.

It has nothing to do with Wi-Fi, imessage is sent whether on Wi-Fi or celltower. I don't think you know what you are talking about.

Imessage only works through Wi-Fi. If the issue persists go into settings-messages and then remove your apple ID and re-add it.

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