The chat penalties are set up with standard durations.
1st = 1 week Silence (unable to use chat channels/social features)
2nd = 1 week Suspension from game
3rd = 2 week Suspension from game
4th = longer and it goes up until license closure. Blizz has never said how long that is. They can also close an account right away for egregious things - such as illegal things.
You did nothing terrible at all - you were not yelling slurs at people, insulting folks etc. The penalty is the same though regardless of the chat infraction.
Now you know and can hopefully avoid it in the future.
For further reading, they have never allowed Advertising in LFG, but they created the services channel to get advertising out of Trade in 2022.
They also put up a recent reminder over on Classic. The Policy is not new, but the Services channel being available is new to Classic.