The maintenance / repair of smoke detectors that are not connected to a building’s central fire alarm system is as you have observed the responsibility of residents.
However your Owners Corporation has apparently regarded fire safety as an important (if not critical) issue in your building, and may have taken the initiative by initially arranging the installation of smoke detectors in each residence.
You should ascertain the detail of the arrangement by which the O/C made the initial installation of the smoke detectors; it may well have been on the basis that it would arrange and pay for the works and then recoup the costs of that and the ongoing maintenance services from the individual Lot Owners.
However so far as this specific issue is concerned, it seems to me that whatever the terms of the initial arrangement may be, as the smoke detector was operating correctly prior to the contractor’s service call, then the cost of the replacement is a matter between that contractor and your strata manager who arranged the visit on behalf of the O/C.
With regard to the “late fees”, if you’re a Proprietor speak with the Secretary of your Executive Committee about what payments these fees may be applied to; they usually apply only to levy contributions, but the detail will be in the Strata Management Agency Agreement that the Strata Manager has with the O/C.