Recovering Old Messages

I about two or three months ago now upgraded to a new phone. Without thinking I switched my new phone over including my WhatsApp to the current mobile that I'm on, however WhatsApp have in the last 6 months or so implemented a feature where you're unable to have multiple accounts for one number. As a result of switching over, I've lost all my messages and history on my old device.

I was researching online and a few posts have mentioned that your phone stores and automatically saves messages, much like a backup or something, I'm wondering if this is true and if anyone knows how to access this? Of course, I'm yet to backup my current conversations as I don't want to lose the messages I have on this phone.

Thanks for reading!