My imessage or text messages don't send only to one person. It works for everyone else in my contacts. Anyone know how to fix it?

2016-07-18T20:08:00Z

I know for a fact that the problem is with my phone because the other person can text me perfectly fine but when I try to reply my texts never go through.

Nick2016-07-18T01:32:39Z

Their phone could be having a problem. Make sure they have "iMessage" on in their messaging settings in the settings app.