They generally believe that nearly everyone living in a western nation will already be in their user database. Ie. your friends will have already uploaded your phone number to them, or you'll already have an account on one of their other products (Whatsapp, Facebook, Instagram).
If you are an adult and they don't have any record of you, then you're probably a fraudster, bot, scammer, or someone else they don't want, so they ban you.
The way to get unbanned is to make sure at least 30 or so friends have your phone number in their contacts list synced to facebook, all with similar names, and then sign up to instagram with that phone number.
I'm guessing you signed up with a burner phone and email address... Well thats not what they want...
If you are an adult and they don't have any record of you, then you're probably a fraudster, bot, scammer, or someone else they don't want, so they ban you.
The way to get unbanned is to make sure at least 30 or so friends have your phone number in their contacts list synced to facebook, all with similar names, and then sign up to instagram with that phone number.
I'm guessing you signed up with a burner phone and email address... Well thats not what they want...