Send an Unpaid INVOICE to Customers to pay

We have a lot of scenarios where we need to send an invoice to customers where customers see the invoice and pay it (same idea as paypal payment as an example).

Example, customers order a big order online and pay for it, then during their event, they order on the phone and ask us to send them an invoice. Another scenario, we cater food for trusted customers who we worked with a lot and the ask to send an invoice for them to pay. 

I know I can make the order online or on the POS and take the payment over the phone using their card, but that is not convenient for so many customers.