Start with the clear cases
List the situations where the answer is always yes, such as a duplicate charge, a service that did not work or a cancellation inside your stated window. These should need no approval.
Set what an agent can decide alone
Name a limit, in money or in time, up to which an agent can refund without asking. Above it, a named person decides within a set time. The limit should reflect how much a mistake would cost you, not what feels polite.
Write the exceptions down
Decide what to do with goodwill refunds, repeat requests and requests outside your window. A written rule, even a strict one, is easier to explain than a case by case judgement.
Give agents the words
Write macros for the common outcomes: refunded, partial refund, not eligible and escalated. Include what happens next and how long the money takes, which depends on the payment provider, so link to the provider's own timing instead of promising a number.
Keep a record
Add an internal note with the reason on every refund. It helps in disputes and shows you patterns, such as one product causing most refunds.