Just to clarify...
If you send SMS from device A to your phone number...Device A sends a SMS, and gets charged for
sent SMS.
Your phone receives an SMS and gets charged for
received SMS.
If you send email from device A to your phone's SMS email gateway address (Example for AT&T your_phone_number@txt.att.net)Device A sends an email and gets billed for
sent data.
Your phone receives an SMS and gets charged for
received SMS.
If you send email from device A to your email account (Example: nobody@nowhere.com)Device A sends an email and gets billed for
sent data.
Your phone doesn't receive anything immediately. When you check your email on your phone, and get charged for
data usage.