I don't use that much in a month as this Internet is used only when I visit my parents' house and stay for a week or so (though I'm staying now much longer because of COVID, less than 1000 people live here so it's safer and also easier to stay locked down).
My use a DSL connection because my mom streams TV shows and that would eat all of the data allowance quickly. She doesn't need speed though, and DSL is fast enough for HD streaming.
This is most likely a technical issue with this base station, since when I had relocated the service to a different city I had no issue with the same SIM card and modem.
Other people too experience it here, but aren't impacted enough to continuously complain.
And yes, that's how most mobile network operators work. There are exceptions, but it's not a "standard" thing even in the EU with the strict consumer protection laws.
And it would reset every month.