Earlier quoted context omitted.
Visa and Mastercard should not do whatever they want, because they are just middlemen in transactions and all their decisions affect their paying customers, much more than themselves. Visa/MC take the money of their customers, who use their cards, by promising to help them pay for anything they want. Visa/MC do not have any right to decide unilaterally what their customers might want to buy (as long as no illegal goo…
As it stands right now they do have the right to do whatever they want. I guess you are proposing that this needs to be changed.
In most cases the customers are forced to accept these unilateral decisions, because they do not have the power to attempt a legal battle with those companies, e.g. for modifying the fees or the data caps.
Nevertheless, even when we do not want or cannot fight such decisions, we should not say that they are private companies and they can do whatever they want.
Those companies are not independent to do whatever they want, they are in contractual relationships with their paying customers.
They may use their power to unilaterally change the contracts as they want to, but that does not mean that we must accept that might is right.