How do I view text message phone numbers sent via iMessage on my ATT bill?
Some text messages that are sent via iMessage are not showing on my cell phone bill. How do I see all messages sent via iMessage on my ATT bill?
iPhone 6 Plus, iOS 10.1.1
Only SMS/MMS messages will appear on your phone bill. iMessages (which are sent to other Apple device users who also have iMessage turned on) are billed as part of your Data allowance rather than as text messages.
More information on the difference in About iMessage and SMS/MMS - Apple Support