Familiarize yourself with their account in the CRM and check the status of their most recent order.

If the order Status is on Hold, make an offer to keep the sale active. If your offers are not accepted, the order can be cancelled and a refund issued.

If the customer is on a trial, they will need to return the product to avoid being charged or accept an offer.

If the customer is no longer on the trial, they will need to return the product to receive a refund. Preferably, they will accept an offer.