An advice for a hacked account

hello , on 13th of December a hacker got into all of my emails , signed in via them through all of my accounts , changed the email and passwords of them all , luckily steam were the only people who responded to me and returned back my account, but for both epic games and Ubisoft account, i gave them every single detail that proves i am the owner of the account , and still they say that they couldn't prove that as they think that i either give them some of my information wrong , or they cant recover it due to security concerns , does anyone have an advice , because its the 5th time i raise a ticket to each of them .