My iPhone 4s randomly stops sending iMessages and only goes to text message?

So I have been texting my friend all day and then randomly my iPhone switches to text message instead of iMessage, like it was using before. I have a strong Wi-Fi connection and I also have unlimited data. My internet works when I go online with my phone, but the iMessage still won't work.

IMessages get converted to text messages when iMessage is not available meaning you might be on iMessage but your friend might not

  • Why is my Iphone not sending as Imessages and receiving iMessages from one person? I'm texting my wife and we both have iPhone's and she is getting the messages as an iMessage but the ones I'm sending her on my end show up at green. Sometime it will go as blue, get the little red exclamation point then send as regular SMS. I'm texting someone else too and she has an iPhone, and she is getting mine as regular iMessages and mine are sending as regular iMessages. Why aren't they sending to me wife as iMessages?
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