is there a way to transfer your contacts and Whatsapp chat history to your new iPhone if it uses a different Apple ID?

my dad forgot the password to his old Apple ID and i've been trying to restore it with Apple support for months now, i've tried multiple times but the recovery process takes weeks and it fails every time. now he has a new iPhone and wants his old stuff to transfer over, most importantly contacts and WhatsApp history. i don't think i can do the standard full backup + restore from backup, because then his new iPhone will have the old Apple ID where he doesn't know the password. i can't do it through iCloud either afaik. there's this software called MobileTrans that apparently provides this function but it costs money and i don't really know if it's trustworthy. i'm not sure what to do now. any help is appreciated!