I created another group for the uk, how to prevent

someone from nigeria from joining the group?

Basically You can't. At least not with certainty

Racist much?

It has nothing to do with it, the racist is the one who considers himself poor because of the color of his skin. If you didn't understand what I wrote, it's not because of skin color, but I want to avoid the area code of the country of nigeria, china, japan, and several others, my focus is to create a group only in the uk .

I specified nigeria, because in the group I had more than 100 thousand users, and several Nigerian scammers started to appear, the group never had limitations, but because of the frauds I'm researching a way to block the specific region

I have groups only of users from Argentina, Brazil, Italy, United States, Dubai and others, I was creating a group for each country.

Well, that's the way Telegram works. It's sad but there is no way to fight against them, at least not with the actual tools that Telegram has right now.

You can enable join requests for your group, and when user joins the group ask them if they are from required country, and only accept of required

Truly sad

Then I'm going to have a lot of work, because I'm going to use Google ADS and Facebook ADS to publish the group.

Why do you think Nigerians are frauds?

I'm not saying they are all, there are many Nigerians who are good, but my problem is that I don't want to mix people up in my group. If my focus is only people from the uk, it will only people from the uk, if my focus is people from the united states, it will only be american, if my focus is canada, it will only members of canada. I'm making a group for each country, and for that I need this control to avoid mixing. Before I didn't even care, but after the scammers started to appear I decided to pay more attention to wanting to separate.