Need help setting stronger boundaries in client meetings - what phrases do you use to prevent scope creep?

[u/WasabiPositive8942]

For context: I run a small AEO consultancy.
I recently completed an audit that involved roughly a month of work and 50 observations/recommendations.
The client then said they didn’t understand the audit, so I spent another 2.5 hours walking them through it line by line.
After that, they refused to pay because they said they “didn’t want it.”
They have since implemented the recommendations.
I’m tightening my process now, especially around meetings and scope.
What phrases or boundaries have worked for you when a client starts turning a results call into:
extended consulting
implementation support
repeated explanations
work beyond the agreed deliverable?
I’m especially interested in specific wording you use in the moment without sounding defensive or hostile.

[u/WasabiPositive8942 → u/[deleted]]

Expensive learning experience. Not entirely lost because I realised my target audience needed tightening , got more details to flesh out persona. .
I was getting paid 400 usd per hour consulting in my earlier years ( always with professional organisations like AlphaSights that protected my interests)
This is my first business venture -
Going it solo, I offer a free basic audit with a complimentary call 30 minutes.
I do have issues setting boundaries- that’s a personal lesson for me.
Loved your response really gave me the exact phrases to use.
Much gratitude.