I’m pretty sure if I accidentally press “OK”, I get charged extra. In addition to the pop-up, I get the same thing as a permanent notification until I reboot – if I try to disable the notification, I get “These notifications can’t be modified”, as it is using the built-in system SIM Toolkit. I am using GrapheneOS. Name and shame: MOVISTAR.
It’s at least partly a holdover from the GSM/2G days, and it serves almost no purpose for end users because every carrier just uses it to try and sell you things you don’t want.