How to Reschedule A Ticket To A Different Performance?

Some of our patrons have been buying tickets online for one performance, but then because of Covid they need to reschedule to a different performance of the same type. Specifically we use this at a museum and a patron bought online tickets for general admission for today, but just called and said they need those tickets rescheduled for next week because of a Covid quarantine. Is there an easy way to reschedule those tickets without having to do a refund and repurchasing? We do not have their credit card on file so we cannot do a refund and then repurchase. 

Any advice would be helpful.