In order to contact PUBG Mobile Support ingame, please follow the steps:

[In-game]
Tap the "Settings" icon at the bottom right of the lobby screen to go to the settings screen.
You can find the "CS" button at the bottom left corner on the [Basic Settings] tap.

[Web]
You can also contact us via web without logging in to the game.
https://pubgmobile.helpshift.com Please access to the site below then you can contact PUBG MOBILE CS.