There is a big push these days for RCS messaging on Android. RCS is Google's answer to iMessage. RCS has a lot of nice features and one major drawback. The major drawback is there are no open implementations of an RCS capable messaging client.
First, you can find out more on RCS from Wikipedia : RCS
The black hole comes in when you have a device with an RCS capable messaging client, then move away from it. Your number is in the system as RCS capable and all the sudden you don't receive messages from a number of users any more. Basically any Android user who has RCS enabled. This gets worse as with Apple's added support for RCS you won't see anything from Apple users who you messages under RCS either.
There is a way out. You have to go to the URL below and input your number for removal. AT&T points to the Google URL so they are likely all connected. No confirmation for Verizon or T-Mobile.
https://messages.google.com/disable-chat
What is very aggravating is this is not documented anywhere. You are happy with a device and texting away. You get a new device and (unknown to you) it doesn't have RCS and all the sudden it seems no one is texting you or responding.
What is needed is an open source RCS implementation...