All transactions made on the blockchain are final and irreversible. The decentralized nature of blockchains means that Phantom is unable to reverse or block transactions once they have been made.
I connected to a malicious website and they stole my tokens!
If you connected to a website that sent you a malicious transaction, you should immediately go into Settings > Trusted Apps and Revoke access to that application. As long as you didn't give anyone your Secret Recovery Phrase or Private Key you should be safe once permission has been revoked.
I gave someone my Secret Recovery Phrase
If you shared your 12 or 24-word Secret Recovery Phrase with a scammer or pasted it into a phishing website, you should stop using this wallet immediately. The scammer now has complete control over your wallet.
Always be careful and never trust anyone asking you to share your seed phrase under any circumstances. Phantom support will NEVER ask you to do this. We advise that you stop using the hacked wallet immediately and create a new one.