Can't receive group messages from iPhone users after switching to Android

Hello,

About 2 months ago, I switched over to Android from iPhone. I love Apple and their products, but I wanted to try something different. About half of my contacts that have iPhones can't contact me in a group message. But some iPhone users can however contact me in a group message.

Here are the things I have tried:

- Deregistering from iMessage using the online tool

- Having iPhone users delete my conversation threads and contact

- Contacted Apple

- Contacted AT&T

- Searched the Internet for solutions.

I noticed most threads about this problem are from 2013, so I was hoping there was a solution to the problem by now.

I also realize this is an Apple, and not an Android forum, but since the issue is regarding iMessage, I posted it here.

Thank you for your time,

Zach