First of all, you have to be an adult in the 2nd generation. To actually call your parent, you need to go to the book icon, select family, select parent, and press B on your tama's parent till it says "phone number." On the phone number the < arrow means the A button, the > arrow means the C button, and the O means the B button. Write the number down, or memorize it, then go to your items and select the phone. There will be circles at the top. Enter the phone number, and the circles should disapear, and your parent will apear in a dialogue bubble, talking, and sending you text smilies.
I hope I helped!