Lost WhatsApp chats after iPhone transfer and iCloud sync

Hello! Not sure if it the correct space to ask. But I really need apples help. I have a business where we communicate with clients at WhatsApp. And I wanted to switch to the new iPhone and transfer all the chats to it. But probably I did something wrong and all the chats disappeared. And empty WhatsApp backup was synchronised to iCloud. So all my chats for the last 4 years got lost. Which is really a big loss for my business. How to contact apple support to ask them to recover the previous backup of chats?