Why won't ny iphone let me change my payment method to none?

I tried changing the country but it wouldnt do anything and i also tried doing it from my
computer on itunes and keeps telling me to put a valid paying method and i don't want that i just want no credit card and i can't get any free apps either because for some reason it still says even on free stuff to fill out the correct billing information

You can't, you HAVE to put a credit card in.