Put a number on revisions. "Two rounds" is clear. "Reasonable revisions" is a dispute waiting to happen.
How it flows
Count each round in the change log. When round two is issued, tell the client in writing that the next round is a paid variation.
Offer the price in the same message. Clients accept extra fees more easily when the price comes with the warning.
Repeat the rule at every stage handover so it is never a surprise.
Stop unpaid revisions by stating the included revisions in the proposal, counting each round as it happens and warning the client before the limit is reached.
Want a daily check on your projects?
Going to the home page in 2:00