Every week like clockwork, the quality will drastically decrease from the usual 100 Mbps, on Saturday to 40 Mbps (minimum for the package) and Sunday to 10 Mbps. This will remain forever on 10 Mbps, even on Monday at 4am.
The only fix was to call the support line on Sunday and ask for a "network reset". Since this is a home internet, it is bound to the cell tower and it is drastically deprioritized elsewhere. The reset deletes and re-adds the device to my tower and sets the tower as the SIM card's home cell.
This was annoying but bearable, I got good at quickly calling and getting it done.
Except starting two weeks ago they refuse to do it, saying they're "not allowed to" anymore. No amount of persuasion helped.
They will report a technical problem and the support people will close it as resolved with a braindead blah response "maybe your signal is bad" or "maybe the tower is busy with traffic". Very sad.
These days I just change the IMEI if the modem and that seems to fix it... For a while.
I also had intermittent disconnection issues with the same ISP that they fobbed off with "maybe your WiFI is bad/has interference" or "you may be running other processes that are saturating the network connection". I had no devices with ethernet ports so I bought a USB ethernet adapter, booted up a barebones linux dist, ran a script that tried to connect to an upstream server, plotted a graph (which showed a disconnection every 20 minutes) and presented that to them. To their credit they admitted there was a problem and moved my microwave antenna to another tower. (For all I know the former tower still has that issue)
Usually ISPs here optimize for lowest possible maintenance cost (right away), which means leaving things in a degraded state forever, and fix it when it finally breaks (which can cost more than fixing it right away).
So in general nobody wants to do a costly fix for one user in a small semi-rural area, especially if nobody else complains (and they don't, they don't know or suffer through it, or have a 10 Mbps package anyway so they don't notice anything unusual).
And it would reset every month.
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.
Disclaimer: I work on one such fork.