Let me ask again the parents question for clarification. Do people really pay for the received sms-es? It sounds like total bullshit, because you don't have an option not to receive sms from a person, like you have with calls.
Absolutely (in the US here). Some carriers will allow you to block all text messages, which can get rid of the annoying ones you wouldn't want to accept, but also forces legitimate ones to get eaten - causing some people to think you're ignoring them when you actually had no idea they even tried texting you in the first place.
Yes, in the US, if you have no TXT plans, you pay for receiving TXT messages.