Problem started maybe about a week ago. I've restarted my phone with no effect. No problems chatting with my iPhone friends through data-based apps like WhatsApp, or Google Hangouts when it's in non-SMS mode.
Let's get you receiving those text messages. Did you recently switch to a droid after having an iPhone? Any new applications downloaded?
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Have those four friends confirmed they have the settings turned on to send as SMS in their message settings?
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