I can't even search for porn on cellular networks and I'm in the US.
Hotels, Starbucks, my job, the library - they all block porn. The idea that kids just have free access to a wild internet is legitimately made up. Schools block that stuff too - universities, even.
As I've said, this solution is not solving this problem because this problem legitimately does not exist. It's solving a different problem. What that problem is, is for you to find out.
My cellular network (Google Fi / T-Mobile), as far as I can tell, has zero content blocking. Hotels used to officially put porn on the TVs via pay per view. I'm very skeptical that they widely block it.
I have high-school aged kids; they all trade techniques for getting precisely that "free access to a wild internet". It's a game of whack a mole, and school IT administrators are on the losing side.
Yes so lets go ahead and burn the entire internet so your kids, specifically, don't see boobies or something.
The reality is that it is YOUR responsibility to control what your kids see. If you fail, I do not care. They are not my kids. Not only do I not care, nobody cares.
You can absolutely lock your kids down and make sure they get no internet access. I know because I grew up without internet. Everything is very much in reach. Do that, or don't, again I don't care.
My mobile carrier blocks porn. I know because I'm an adult and sometimes I want to watch porn, and I have to use a VPN.
What you should do is call up whoever you are giving money to for internet and ask them about blocking. If they tell you they don't offer that product, then you, as a consumer, should cancel your subscription and go to another carrier.
I… very much doubt that.