Hi @RW11!
What phone model are you using? You can find this out under Settings > About phone > Phone model.
Regarding texting, this is done using the preinstalled Messaging application. More information can be found in the user guide for the phone. The link below is to the guide for the Xperia XA, let me know if you are using another phone and I'll send you the relevant guide.
http://support.sonymobile.com/global-en/xperiaxa/userguide/Reading-and-sending-messages/
Let me know if you have any further questions!
