Sending SMS to Numbers with Five- or Six-Digit Short Codes Are Bounced
Ultimately, the solution was to decouple my Sprint number from the Google Voice service. The instructions to stop using the Sprint number are at https://support.google.com/voice/answer/1207070?co=GENIE.Platform%3DAndroid&amp;hl=en. It says, 


  Stop using Google Voice on your Sprint phone
  
  I use my Sprint number
  
  Use a computer to remove the Sprint number from your account.

On your computer, open Google Voice.

At the top left, click Menu Menu and then Legacy Google Voice.
Google Voice will look different, but you're in the right place.

At the top right, click Settings Settings and then Settings. Click
the "Phones" tab.

You'll see your Sprint mobile number with the note "Enabled by
Sprint." Next to your Sprint mobile number, click Disable.

After you turn off Google Voice, you'll have to record a new
voicemail greeting for your Sprint phone service.



Now I am able to text those five digit and six digit phone numbers and get a reply back using my stock messaging app without an error!