How to ensure the ban of three individuals

Block and report and find another match. Xbox enforcement will deal with the report. Best not to engage or you may be subject to enforcement as well.

Your best course of action is to report the player.

File report

File a complaint on Xbox One

If you think a player has violated the Microsoft Code of Conduct, submit a report to Xbox. You can report a player’s behavior, or specific content such as Club or LFG messages and activity feed items.

All reports include the option to enter comments. Use this opportunity to provide us with more information about the violation.

Report a player

To report a player who has behaved in an inappropriate way or posted inappropriate content:

1. Press the Xbox button
   on your controller to open the guide, go to People, and then select the gamertag you wish to report. If the player is not a friend, select
   Recent players, or select Find someone and enter the player's gamertag to search.
2. From the player's profile, select Report or block.
3. Select Report.
4. Select one of the following reasons for the report:
   • Player name or gamertag: The player's name or gamertag is inappropriate.
   • Cheating: The player used unauthorized modifications or attempted to gain an unfair advantage in multiplayer gaming.
   • Player picture: The player’s gamerpic is inappropriate.
   • Voice communication: The player used inappropriate, abusive, or threatening language in voice communications.
   • Unsporting behavior: The player didn’t show good sportsmanship.
   • Quitting early: The player frequently quit multiplayer games to avoid losing.
5. Select Add comment to provide more information. When finished, select
   Report.

Report someone in a message

To report someone who has sent you an inappropriate text or voice message:

1. Press the Xbox button
   on your controller to bring up the guide. Navigate to Communication, and then
   Conversations.
2. At the bottom of the message, under Reply, select More.
   
3. Select the reason for the report (the options are the same as in the previous section).
4. Select Add comment to provide more information. When finished, select
   Report.

Messages in Club chat can be reported to either a Club admin or to Xbox. If the message doesn’t belong in the Club, select
Club admin. If the message violates the Code of Conduct, select
Xbox Live Policy & Enforcement Team.

To report an inappropriate Looking for Group message:

1. Navigate to your LFG post.
2. Select the text showing how many players are interested.
3. Select the gamertag with the inappropriate message, and then select Report message.
4. Select Inappropriate message.
5. Select Add comment to provide more information. When finished, select
   Repor

If you haven't already, you would need to file a complaint on them via the console. https://enforcement.xbox.com/en-US/home/howto#sub-topic2-0

I don't understand how this works because I was banned twice in a row by the same person within three days.

Each message can be treated as an individual action. Multiple messages can bring multiple enforcement actions.

Just like if I were running stop signs in my car, each one is a separate offense.

If it were free then banning users would not prevent them from repetitively re-accessing the service. The DRM and the paywall + the various apps locked behind it ensures they will suffer a financial loss every time they attempt
to create a new membership after a ban. It helps to ensure that the majority of unfavorable individuals remain exhiled from this prestigious community.

[quote user="THEOWENKILLER"]

Because you are posting on a public forum that i have every right to reply on if i so wish.

[/quote]

Posting is a priviledge.. not a "right"