Switching apps shouldn't mean losing your history. You can import a WhatsApp chat one conversation at a time.
On Android
- Open the chat in WhatsApp, then tap ⋮ → More → Export Chat.
- Choose Include Media if you want photos and files.
- Pick Pralaap from the share menu.
- In Pralaap, turn on Import Chats and select the contact to map it to.
- Tap Next and confirm.
On iPhone
Open Contact Info or Group Info in WhatsApp, tap Export Chat, choose Include Media, then pick Pralaap from the share menu and follow the same steps.
Before you confirm
Messages keep their original timestamps. The contact you choose can't be changed afterwards, so check it twice.