How do I text with a phone number only. I keep getting despite entering the 10 digit phone number

[AC Question]

I put in the ten digit phone number but keep getting send errors

 

[B. Diddy]

Welcome to Android Central! Are you sure this is a cell number, or a number that can accept text messages? Can you text to other numbers without problem?

 

[ManiacJoe]

Which phone?
Which version of android?
Which carrier?
Which SMS app?

What is the exact wording of the error message?

Have you verified your APN settings with your carrier or their website?