Apple ID changes

Hello, I do have a question: I changed my Apple ID but In my phone I can still see the old one when we open settings, meanwhile when I open line "Name, Phone numbers, email ... then I see "contactable at'' and on the first line there is written my new Apple ID. So please, let me know what is the problem that on the first page of Apple ID, on the top has not changed the old one into new one yet?