I got banned and I don't know why

The only folks that can help you are
https://enforcement.xbox.com

They do not monitor support forums. You may be able to request a review

Despite what some may claim, XBLPET will never ever ban anyone “for no reason”. Suspensions
always occur as a result of a specific Code of Conduct violation.

You can log in on this page and find that information:
https://enforcement.xbox.com/Enforcement/ShowEnforcements


Sorry, but no one here on the forums can address issues dealing with enforcement actions.

You will need to visit Xbox's enforcement page to find out any information about your current case.

Here are some links that might be useful for future reference.

Link 1:
https://enforcement.xbox.com

Link 2: https://enforcement.xbox.com/en-US/home/howto#sub-topic0-5

Link 3: http://support.xbox.com/en-US/xbox-one/xbox-live/enforcement-on-xbox-live

Link 4:
https://enforcement.xbox.com/Enforcement/ShowEnforcements


Link 5:
http://enforcement.xbox.com/home/staysafe#topic0

You will need to go to https://enforcement.xbox.com and sign in with your suspended gamertag.

Then click on the yellow/orange tile with the hammer icon, and check the list of suspensions.

Be aware, that you can only complain about suspensions that are LESS than 12 months old.

Check if there is a currently active suspension. If you think that this active suspension was made in error, you can file a Case Review by clicking the appropriate link. (only if it is more than 24houres bann)

You'll have to fill out a small questionnaire that tests if you have understood the Code of Conduct. If you need a
refresher about the CoC, you can click here.

Then after you passed the test, you can send a message to the Enforcement Team.

Be warned however: You only get one chance to have them review the case! Each report that is being sent in, causes the consoles involved to collect data and telemetry which is sent in along with the report as evidence. For example a text
message you sent. Based on that evidence, the Enforcement Team decides if a suspension is warranted or not.

Since you got a suspension, they do have evidence of you breaking the Code of Conduct in one way or another. So do not waste your one and only attempt by sending them a message that basically says something like "But I didn't do anything".

You would need to go to the enforcement site HERE for info & to file for a case review if eligible.

For information about your ban and to see about submitting a case review, you would need to go to http://enforcement.xbox.com