You can use Verizon Messages to integrate the tablet into the phone, but the tablet cannot send and receive texts by itself, as you need an actual phone with a number to integrate with. So, sending and receiving using the tablets service line number won't work.
You need to sign up for integrated messaging. The text will still come through and be sent from your mobile phone number, they will just appear on your tablet.
The tablet has its own number so you can access data while on the go, like a cell phone. However it does not support its own text messaging.