My cellular data rate was suddenly uncapped?

Alright, a bit of context. I pay about 2 bucks a month for an unlimited data plan, the caveat is that its on the slowest speed available. I dont particularly mind this as it's good enough to send text messages and I rarely need to use it anyway. Except when I'm on holiday (which is right now), when I'm stuck with a connection of 0.03 mbps down and 0.01 mbps up. Not exactly an issue, as I can wait a bit longer for stuff to load (been loving compact reddit btw, its great. If you ever need a lightweight version of reddit, add /.compact at the end of the url)

Anyways, I was waiting for discord to load yesterday when my connection to the cellular network suddenly dropped entirely. I'm not sure what caused it, but I know it was at 1am (I think on the spot, so there may have been some automated system that dropped every device off the network). After I got reconnected, my speed was suddenly uncapped to 16 mbps down and 1 mbps up. Initially I thought this was because there was no one using the network, but this morning I woke up with the same uncapped speed. I rebooted my phone and now it's back to the capped rate of 0.03 mbps.

My wifi has been disabled for a couple days now so I couldnt have connected to a hotspot (which I dont think couldve turned on either way, as everyone was asleep).

I looked around and no one seems to have experienced anything like this. What caused this to happen (or rather, what are some possible causes to this)? I'm incredibly confused and would love some explanations. Thanks!