Losing 500 sales per day

A client reached out to us for solving a problem they have : Up to 500 sales are lost per day due to many reasons like insufficient funds and other reasons They asked for a system to help them call customers and finalize the purchases. Is this the only solution to offer or is these something else we should do for them ?

Thank you for your honest response

Edit : they are making actual sales other than those 500 lost ones They have cart recovery emails setup for recovering those sales with promotions