Q: deregister

Hi parkyeo3,

Thanks for checking the Apple Support Communities! I understand that you're having trouble with receiving messages from your friends who use iPhones after deregistering your phone number from iMessage. I use text messaging to keep in touch with everyone so I can understand wanting to make sure you're able to receive your messages and I'm happy to provide some direction. 

It looks like you've gone through all the right steps for deregistering your phone number from iMessage. One thing that you'll want to make sure of is that your friends are sending the message to your phone number and not your Apple ID email address which can be used for iMessage. This could cause it to appear as though you're still using iMessage. If your friends still can't message you, you may want to have them delete the message thread to you on their phone and then start a new one and try again. 

If you still can't send or receive texts after your deregister iMessage

If your friends and family have issues sending and receiving texts from their iPhone, iPad, or iPod touch, ask them to delete their iMessage conversation and create a new one. To delete a conversation, swipe left on the conversation and tap Delete.

When you delete a conversation, you can't get it back. So make sure to save any important information from the conversation.

Get help if you can't deregister iMessage

Also, if you've just gone through and deregistered, it may take a few hours to go through. 

After you complete deregistration, your phone number is removed from iMessage services. You should be able to receive text messages right away but it might take a few hours for some Apple devices to recognize that you're not using iMessage when they send you a message.

Deregister iMessage on your iPhone or online

Cheers!