IPhone :: Prevent It From Using Text Message With An IMessage?

I would like to know how I can turn off iPhone's iMessage system and just send regular text messages to other iPhone users.Here's why.On two separate occassions I have missed a date with the same guy because we would send each other messages, and get no reply. Why? Because the iPhone appears to choose to send it as an iMessage.But because one or the other isn't connected to a wireless port at the time it doesn't go through.so we're both waiting for the other to reply and it never happens.So we assume the other is asleep, phone died, whatever and plans are automatically cancelled.We take the train home and then iMessage floods both of our phones with 30 minutes worth of texts.

I would like to have the ability to send a text as a text message, and only send an iMessage when I choose it to be the wiser of two methods of sending a text.iMessage is not my preffered method of sending a text because it doesn't work as well.It does a terrible job of letting me know when it can't send and it utilizes wifi which is less abundant than the network I'm on.Moreover I have unlimited texts with my plan.So I don't understand the point of a phone automatically trying to send texts through wifi when it doesn't work as well,inadvertantly cancels my date twice, and leaves me bitter and ALONE at home again.So do I have an option to just send texts as regular texts? Or is this a new feature that I can't control?