Nothing I can think of.
Provide the 10% referral discount without me calling in.
Perhaps provide a follow up call to verify if the treatment worked.
As far as I can see right now no improvement is needed.
There was a bit of lack of communication between the person who took my booking and the onsite tech, leading to the tech not arriving with a ladder and needing to use mine. Had I not been at home (the booking rep said I didn't need to be there), the work may not have been able to be completed, or at least not to the same quality.
When checking site, checking in with the site manager to ensure good communication would be a nice to have.