How do they withdraw money from the balance when going to the site?

Question

Information Security

Hello!
Yesterday, on a smartphone, I clicked on a banner on one of the sites. The ads on the site were from the Google ad network. After a couple of seconds, I received an SMS stating that a paid subscription for 50 rubles was connected. The amount has been debited. The subscription appeared in the Megaphone application, some kind of paid video service. No applications were installed at that moment and nothing was downloaded, there were only a few redirects. The smartphone was connected via a megaphone network, not wi-fi.
How is this possible? Is one transition enough and without our consent through a cellular communication channel they can withdraw money from the balance? How do scammers get a phone number? Somehow scripts pull data from cookies or is something transmitted through the communication channel? Can you protect yourself from this?
update
There was no confirmation request. The money was debited immediately after clicking on the banner.

Answer 1

The passed stage, it is written in small print that money will be debited during the transition. So call Megafon (so-so operator) and say that you want a separate account for paid subscriptions, and that's it, there will be no more extra charges

Answer 2

Hello, Happy Holidays!
It's not about cookies. Your connection is handled by the mobile operator, they deduct certain amounts when you click on certain links.
If you follow the same links through a cable connection, they may either be blocked or ... free :)
Thank God, the 00s are over, but some people just don't want to put up with it.

Answer 3

The phone number is given to them by the operator. Formally, there should be a form with information from the subscription, a button yes I agree to all and further in the text. But it’s clear, I don’t want to offend anyone, but there are no adequate people who subscribe to something in this way, so all these schemes are pure water. IMHO, this model should be banned for a long time, as well as the transfer of a phone number by the operator to sites.

Answer 4

it’s possible to
google for dealers on “pseudo SMS subscriptions”
many or all have
parental protection - a tablet, their own - disable - OPSsos allow a period without a fee, and some completely unsubscribe from this, success is variable,
do not google without adblock, protection is variable