overcharged my client - can I reimburse over Rover?

Call Rover Support at [Edit: Rover’s contact options have changed. Visit the Rover Help Center at https://support.rover.com/ to find the phone number, help articles, or chat with the team] or use the Help/Contact link at the top. They can process an adjustment to your client's credit card.

Or if it is a frequent repeat client, you could offer to just discount the next visit by $15.