How Do We Regain A Hacked Whatsapp Account

Hello guys,A family member's WhatsApp account was hacked yesterday.The hackers still have possession of the account, and she has been unable to log in since yesterday.The hackers have been calling her contacts to extort money from them.Please, as a matter of urgency, how can we regain access to the WhatsApp account.Thanksps. We have been trying to reach WhatsApp customer care.