I can certainly understand why this is frustrating and I definitely want to get this fixed. Are you receiving an error when sending a text to this contact? Are all your other texts being delivered to everyone else? Is the contact that isn't receiving your texts also a Verizon user? Please share more details so we can better assist.
Follow us on Twitter @VZWSupport
If my response answered your question please click the "Correct Answer" button under my response. This ensures others can benefit from our conversation. Thanks in advance for your help with this!!