I have recently upgraded my mobile to Samsung Galaxy S24 Ultra. I kept my old S21 Ultra, with the idea to use that for personal things and my new S24 Ultra for business.

I had WhatsApp Business, installed on my old mobile, linked to my old mobile number. I have since ordered a new SIM card, which I wanted to put in my old phone, to create a work-free SIM/number to use for personal, away from my work.

I factory reset my S21 Ultra, and when trying to register WhatsApp, it allows me through. As soon as I send one message, it immediately blocks the phone, saying "This account is not allowed to use WhatsApp due to spam" (chats are still on this device).

Despite factory reset, how do I permanently delete my old chats from old SIM/number so I can use WhatsApp on new SIM/number as hoped?