A phishing text through telegram from my brother's account, how to disable access?

Received this text from my brother's telegram account, but he has not sent it, and this text doesn't show on his side. Other people in his contacts received the same message. Understood its a phishing attack and his acc has been hacked. Told him to check his devices logged in and it showed his mobile, laptop and desktop and no other suspicious device. How to get it removed completely from his telegram acc? And how does this attack work? few people who clicked the link said it asked for their ph no. https://preview.redd.it/dba9xpg803je1.png?width=184&format=png&auto=webp&s=e33cd1c658f72b8bf1bb7f15160186b36803ff4f