disconnet someone from using my Direct TV streaming services

You’ll have to reset the password with the email address. From there, change the address associated with the account and file a fraud case if necessary.

Do you know ‘who’ took your password? Was it given to them?

Just change the password--that should be enough. U don't need to change your email address.

People keep saying that if you change your password it logs off all devices that are logged on.  Does anyone know from personal experience that this actually happens?  In my (very limited) experiment, it doesn't appear to.

At one point in the (distant) past, Customer Service had the ability to reset an account in such a way as to "bounce" all logged in devices.  Reports are that they deny being able to do this anymore - again, I don't know if that is true.  It would seem there should be some way of doing this (since they can disable accounts), though it isn't clear that providing the capability directly to an end user (at least without some control on it) would be a good idea.

And no one can "take" a password - it had to be shared in some way with others for this to happen.  So the simplest answer is never share your login credentials - but of course that doesn't help after the fact.