I recently gave my brother my Sim card for my old Apple phone I think he has my account information what can I do

I'm guessing that if this is from an old phone that it is an inactive SIM. Is that correct? While the SIM has your cellular account information on it, I'm not sure if it can be read to get anything someone might need. What makes you believe they have some of your account information? It's your brother, ask him.

To the best of my knowledge, about all they can get from it is your phone number. If the SIM was ever used in a non-iPhone, it's possible that it has contacts. What it does NOT have is any information on your Apple ID. If you have another phone and SIM active on the mobile number that SIM was used with, it's useless.

The SIM doesn't contain any of your Apple ID information. If he has access to your Apple ID, he got it some other way. Change your passcode.

what are the dangers of someone getting an old sim card anyway? can they get a lot of information from it?