I recently switched from my iPhone to an Android. Before removing my SIM card, I disabled iMessage in settings. My Macbook Messages app shows it as disabled, and the online service to disable a number does as well. When iOS users send me a message directly, it is sent as SMS. However, when I am added to a group iMessage it doesn't change to MMS. Any ideas?
I found out that deleting the conversation history and starting a new one caused it to use MMS. Still hoping there's a general solution to telling everyone to delete their history.