Our owners have paid the property management service fee, so why should we charge the housekeeping service fee? Is this a double charge?

These are two different fees. Property management fees are paid by everyone in order to maintain normal and reasonable expenses such as cleaning and public security in the community. Domestic service is a convenient service provided by residential property, of course, this is extra. It's a bit like, your family hired a nanny, don't you pay the nanny extra?