Can't talk about wholesale mobile network capacity pricing, but what you experienced is quite rampant with pretty much all services. They count on you to be too lazy to look up the information, and too lazy to actually do the switch. (And it works, with vast majority of the people)

I had the same with my ISP - currently I pay about $60 for 10 Gbps connection. Before I switched, I paid about $130 for 200 Mbps, years ago...

A few months ago I reviewed my bills from Godaddy, and it turned out that they have hiked the price of my domain every single year since I've had it. I switched to Porkbun, and now I pay half (the same that I paid to Godaddy, when I bought my domain 10 years ago...)

Switching bank will be a bigger bite, but I'm preparing for that too...