Konami complaint: Game account got hacked and the company is not helping to retrieve the account back.

Konami is a japanese based company and they have several games, one such game is eFootball PES 2021 which i have been playing since last 4years, it is the only game i play on my mobile phone. Yesterday night my game account got hacked and i was immediately logged out of my game. I was panicked and try to login my game account but realised it was hacked and the person who hacked changed the Mail ID and Password of the game account. I immediately reported to the Konami website and wrote them in detail, i also received a mail from them asking me to im the owner of the account and asked several proofs and screenshot, i mentioned everything they asked. as i had so many purchase history too with the game, i attached the screenshots of the Purchase i made through app store and mentioned everything which states im the owner of the account. But they sent me a mail telling account owner is responsible for securing owner ID and password of the game and said sorry they cant help me.
Im already feeling so much devastated as the game account which i have been playing since last 4years is hacked now and this company is also not ready to help their customers who have been using their service from long time and has purchased so many items through in-game.