Switching Text Chat and Speech Texting
When you open Messaging and click the + button to start a new chat thread, Windows Phone will ask you to select a contact. If multiple options are available, you will then have a choice of which chat method to use.
For instance, your contact might have a mobile telephone number and Facebook listed. Their Facebook status might be offline, however, so you would select the mobile number, and then send a message as normal.
If you don’t want to use your hands, once you’re at the point of entering your message text, simply tap the Speak button (a microphone icon) and intone a few words to send to your contact. Note that this requires an Internet connection to work successfully. This feature seems to work pretty well, and is certainly faster than typing!
When you receive a message back, your contact might have since logged into Facebook, so you can continue your chat with them by tapping the Switch button, identified by two opposing arrows. You will have a choice of what service to switch to and then be able to carry on chatting.