the code can be read over, copy-pasted-transmitted... this method proves that the user has access to the phone number but not that the current device "holds" it

I am not asking for such api, I know it doesn't exist. im asking for other means to verify that the user entered the number on the phone it belongs to. And in this case, this is not a privacy fail, because the user surrendered the number willingly, and I just want to know if he didn't lie