Netflix changed my subscription to premium without asking. Can that be?

Actually I have the abbo where 2 people can watch at the same time. Today I will email you that Netflix has set my abbo to premium where 4 can watch at the same time and ultra hd. I didn't want that and now I have to pay more for this month

No. Just put it back.

Possibly change the password, maybe someone got unauthorized access?

Actually I have the abbo where 2 people can watch at the same time. Today I will email you that Netflix has set my abbo to premium where 4 can watch at the same time and ultra hd.

Have you (or someone who has access to the account) possibly also let others look or passed the data on, so that sometimes more than 2 positions looked at the same time?

Netflix is not stupid either and is aware of it. I could imagine that that was the case and therefore (consequently) upgraded you, since several devices / people used it at the same time…

Nothing changes that I have to pay more for the month

Well that is not logical. Only two people are allowed to watch, that means if a third netflix starts it should be the case that Netflix says that it does not work and does not simply change the subscription. Because we can't know who is watching when, it may be that 3 people wanted to watch at the same time

No you don't have to. For me it also switched to 11.99 euro several times although I didn't want it. I just put it back.

Finished. No more than 8 euro were debited.

Because we can't know who is watching when
there it can be that 3 people wanted to watch at the same time

Then you have to pay the price for it.

Sure, there are different ways that Netflix could handle it. You could then display a message at 3. ("2 films are already being watched with this account") or you could simply "kick out" another one when another person registers to watch.

But they just chose the path, which also brings them more money.

It is up to you to make sure that you do not exceed the limit.