Show exactly what returned
Gather the prior invoice and ask what was cleared, where the restriction was found, and what test followed. Add your observations: the first wet location, time from startup to the drip, operating mode, any visible ice, and whether the problem is steady or intermittent. Photos from before and after the prior service are especially useful. Do not reproduce the leak just for evidence.
Ask the technician to follow water from its collection point to the final outlet. That should include the pan, connection points, hose route, and any pump, not just the accessible end. Have them distinguish water escaping from the drain system from moisture forming on another surface or water associated with icing.
For example, Mitsubishi's SLZ-KA cassette installation instructions require a drainage test and checks for leaking joints. The exact installed model governs the method; a homeowner should not perform that installer test. Mitsubishi SLZ-KA09/12/15NA manual.
Ask for proof of the fix
We would want three things in the service record: the source found, the correction made, and the result of the completed test. If the technician finds an airflow or refrigeration problem instead of a drain restriction, ask for the measurements supporting that conclusion. “Drain clear” and “leak resolved” are different findings.
Ask how long and in which mode the system was checked. An intermittent leak may require conditions that were not present during a short visit. Discuss a safe follow-up plan if the technician cannot reproduce it, including what you should record and when to stop operation.
If the original repair did not solve the same reported problem, ask the provider to explain any return charge and the applicable written service terms before approving more work. That is a request for clarification, not a guarantee of free work.
Your next step: Send the prior invoice and current evidence, request a leak-source investigation, and keep the head off until the provider gives a safe operating plan.