someone is trying to use my apple id on an unknown device dhoukd i change my password?

You most certainly want to change your password but in case your Apple ID has been compromised you should review the information in this link to ensure you take all possible measures to re-secure your account. Please be sure to sign out of any Apple devices you are currently signed into before making any changes to the account information. Additionally you will want to go to appleid.apple.com and make sure to review all of your information for any changes that may not have been made by you personally.

If you think your Apple ID has been compromised - Apple Support

Hope this helps!

Hey there.

Go to https://appleid.apple.com/#!&page=signin

Then login with your current details and then go to Security Page and there is Change Password option.

Hope it solves your problem

Ah ... just saw what you mean. Yes change your password for good!