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Did they recover refrigerant and remove the coils to clean them?
Coils should be removed and cleaned as if there was mold on contaminants, it has most likely been drawn between fins of coil also.
It is also a good idea since unit sounds like it is located in a somewhat damp area, to have them install a uv light in the duct to prevent regrowth.
The uv light should be on return side or just above coil.I would suggest you have him remove coils and clean them.Also make sure the ducts are actually clean.Ask them to show you inside the ducts .Most people who clean ducts have cameras that allow you to see the results.If mold is still growing, make sure cfms on air handler are correct.