Schedule B charges are a very common way for strata managers to pump up their charges or cover their costs (depending on which way you look at them).
The weasel words here are “upon instruction” because if at any time your committee has asked the strata manager to take care of correspondence, for instance, that would be considered an instruction that would cover every instance.
What you need to do is ask for an itemised invoice of their charges and then conduct an audit of what they are doing and what they have been specifically asked to do.
If they are handling a lot of issues that they haven’t been contracted to do, then you should ask for those to be itemised in your bill (although that might in itself attract an extra charge).
And your committee might want to instruct them not to do any more than the very specific jobs that they have been hired to do. But then the question arises of who will make the extra calls and answer the additional emails.
What you really need is a bit more transparency and there are a lot of software packages the strata managers can use that would allow that without any additional burden on them or cost to you.