The key thing is to photograph your meter right away and take screenshots of your receipts as soon as you notice the water's been shut off. Then file a complaint with your management company or service provider - but do it properly, in two copies, and keep one for yourself with a receipt stamp on it. List the exact dates and times of the shutoff and attach your meter readings. If there's no hot water at all in the house, not just low pressure, that's considered a more serious reason for a recalculation.
In your complaint, specify what period you're demanding a recalculation for and what amount, based on the tariff. The organization has to look at it within some timeframe (usually two weeks), and if they agree, they'll do the recalculation on your next bill. If they refuse, you can complain to Rospotrebnadzor or the housing inspection - they put pressure on utilities way more effectively than personal letters do.
Honestly, a lot of people just pay as usual because they don't know you can demand a recalculation. And the management companies are counting on people being passive. My friend managed to get a refund that way - she filed a complaint and they recalculated for two months when they had water problems at their place.