If you have an AT&T phone with text-messaging capabilities, you may be able to send an SMS message from your mobile phone to a landline phone during times that you cannot converse verbally. Your SMS message will be converted to a voice message as soon as the receiver answers the call. Sending a landline text message is relatively simple, as it is done in the same manner that you would if you were sending out a regular SMS message.
Open the "Messaging" application on your AT&T mobile phone. Select the option to compose a new message. Enter the recipient's landline number in the "To" field.
Enter the subject for your message in the "Subject" field, followed by entering the content of your message in the body of the message.
Proofread your message (optional) and select the option to send the message to the landline phone.