This is my code. But I want it to display "Enter a valid phone number(Like: 044-42046569 and enter a valid phone number in the phone textbox if I enter a text which is more or less than 12.

Billing Address

Step 1: Enter your name, address, and phone number:

Name: Address: City: State: Zip: Phone:

Step 2: Select the size of pizza you want:

Small Medium Large

Step 3: Select the pizza toppings you want:

Pepparoni Cheese Pineapple Chicken Pepparoni Pepparoni