Hello Toffie
The strata manager has not handled this well. From reading your post, I assume that English is not your first language. The strata manager should take the time to explain the situation clearly. Would it help to get a friend to talk to the strata manager on your behalf?
If you are in NSW, the law is the Strata Schemes Management Act 2015. Section 107 COMMON PROPERTY MEMORANDUM helped me answer your question.
The common property memorandum is a list of what is your responsibility (as owner) and what is the owners corporation (strata) responsibility.
For intercom systems: If the unit is inside your lot and the wiring / unit only services one lot, then it is YOUR responsibility to pay for it.
If the unit services more than one lot, it is the owners corporation’s responsibility. For example, the unit outside the building, which everyone uses, is the owners corporation’s responsibility.
The strata manager should have told you this BEFORE sending someone to fix it. They should have said “you have to pay for the cost of fixing or replacing it.”
Did you send emails and SMS messages to the strata manager? Did you write something to say that you would pay for it? I don’t know if merely asking the strata manager to send someone to your home is the same as consenting to paying for the work.
The strata manager may threaten to charge interest on the outstanding amount if you don’t reimburse them now. I don’t believe they are allowed to do this unless they go to court first. A lawyer could answer that question.
You should talk to a strata lawyer. Just be aware that lawyers cost money. The lawyer might cost more than the new intercom.
You should at least arrange for mediation. Mediation is free.