To cancel a user's virtual phone number follow the steps below:

1. Go to the section titled "Customers"
2. Search for the user in the search bar
3. Click on the user’s username to view their account
4. Click on the section titled "Virtual Phone Number"
5. You will find a button titled "Cancel" next to the phone number
6. Click on the Cancel button to cancel their virtual phone number  

When a customer cancels their virtual phone number, they will be charged a pro-rated amount for their usage starting from the date on which they subscribed.