How do I block an incoming phone number from messaging me if they are not a MySudo user?

There are a couple of ways to block an incoming phone number from messaging you:  

Option 1:

• Tap the Menu icon in the top left corner
• Tap Settings
• Tap Calls
• Tap Block List
• Tap Block Caller
• Select the contact you want to add to the Block List 
  - to remove that contact from the Block List, tap Edit > tap the red icon > tap Unblock

 Option 2  

• From within the text conversation, tap the ellipses (...) in the top right corner
• Tap Details
• Tap the > next to the contact again
• Tap Block this Contact (if one of your contacts). Tap Block this Caller (if not one of your contacts) 
• Confirm Block Contact  

You can also reset (change) your number if the annoyance you are receiving warrants it.