I may be wrong but I believe Owners Corporation manager is a Victorian term. Is your strata manager based in Vic? The usual terminology in NSW is strata managing agent.
This is important because strata tax laws are different for NSW and Vic.
Also, unless your strata scheme is earning income above and beyond levies, then you are not subject to making a tax return except to say “Nil tax”. If that’s the case, this sounds like a nice little earner for doing next to nothing. Ask your strata manager exactly what it is that they have done that you are paying for.