You can now send text messages with your Amazon Echo! At the time of this post, the feature is only available for Android users.
Amazon has expanded Alexa’s ability to send messages beyond the Echo to Echo and Echo to Alexa app feature that Alexa Calling and Messaging originally brought us. Now you can ask Alexa to send anyone a text.
Here’s how to set up Alexa SMS (Text) Messaging:
1- You have to first set up Alexa Calling and Messaging, click the link for instructions.
2- In the Alexa app on your phone (this must be the phone you plan to send texts from, as this is the number that will show up when you text people), click the Conversations icon 
3- If you are not automatically prompted to enable SMS, click the Contacts icon at the top right (the little person). Then under your name, click My Profile.
4- Scroll down to Send SMS and tap the switch to turn this feature on.
5- Click OK to accept the terms.
6- Click Allow to allow Alexa to send SMS.
To test this, turn to your favorite Alexa enabled device and say “Alexa, send a text.” She will ask who you would like to text. This should be the name of a contact stored in your phone. If you have added members to your Amazon household, she will ask who the text is from. Each member of the household will have to set up Alexa SMS on their own device. Next, she will ask for the message. After a brief pause when you have stopped talking, she will confirm that she is sending a text from your phone.
You will see a new text sent from your phone with the transcript of what you said as well as a link to a recording of you saying it.