Checking if a guests phone number is a VOIP Number
Step 1: Go to phonevalidator.com
Step 2: Enter the guest phone number and click "Search"
This only works for US phone number. Please enter the number without the "+1" in front of it.
Step 3: View the phone line type
If it says "VOIP" then the number is a VOIP number. If it says anything else, it is not a VOIP number.