This happened to me. In the beginning, I was paying $35 for 25/5 through Comcast. It was fine, did everything I needed. But then, roughly once a year, for a few years in a row, they would announce a speed increase on my plan, complete with a flyer in the mail congratulating me on being a loyal customer while patting themselves for being such a fine, generous company.
A few months later, like clockwork, a plain black-and-white letter would be attached to my bill informing me of a change in the price of my plan due to unspecified business and economic factors.
I am literally on their lowest plan, and still pay over $60 a month. That's more than what I pay for 3 cell phones.
It's fucking sleazy and I would gladly switch ISPs yesterday if they didn't have a government-granted monopoly in my area. (And no, Starlink and T-mobile are not options for reasons I don't have time to get into right now.)