T-Mobile allows you to send text messages to other T-Mobile customers using its My T-Mobile Text Messaging tool if you are a T-Mobile subscriber. Although it doesn't cost you anything to send a text, the receiver will pay standard fees to receive the text on his T-Mobile phone.
Navigate to the T-Mobile website in a Web browser and log in to your T-Mobile account.
Select "Email and text tools" under the Mobile Life heading.
Click "Send a text message."
Fill in the To and From fields. Type your text message in the Body field.
Your message can be a maximum of 129 characters long.