Why can't I receive group messages from iPhones?

[AC Question]

I recently switched from an iPhone 5 to an LG G4. Before switching, I turned off my iMessages and also deactivated my phone number from iMessage by contacting Apple. Although I have not had any issues receiving text messages from iPhone users, group messages are a problem. I am in a group message with my mom and sister, and I do not receive any of my sister's messages. Her phone is still sending the messages through as iMessages and does not give her the option in group messages to send as a text instead. She removed my number in her contacts as an iPhone and instead switched it to the general "mobile" category, but we can't figure out what else to do!

Any suggestions would be appreciated!

 

[Almeuit]

I use a 3rd party app but look in the settings of whatever app you use for messaging and ensure "Use MMS For Group Messages" is checked. I have this checked in my 3rd party app (ChompSMS) and it has no issues with group messages anymore.

Also ensure your friends have SMS messages allowed -- if they're using nothing but iMessage then that could be another issues.