Simply open your console by pressing the ~ button on your keyboard.
Copy one of these lines and change 'YourNameHere' to your own name that you are using.

A fun thing is, you can do this to whatever you want to say. It doesn't have to be a case opening message or a ban message, you can do whatever you want.

Example:
playerradio Radio.WePlanted "
WHOLF
has opened a container and found: YO MAMA ON DA DANCEFLOOR"

• playerradio Radio.WePlanted "
YourNameHere
  has opened a container and found: ★ StatTrak™ Karambit | Lore"

• playerradio Radio.WePlanted "
 Yournamehere has been permanently banned from official CS:GO servers."

Example: playerradio Radio.WePlanted "
WHOLF
has opened a container and found: ★ StatTrak™ Karambit | Lore"

List of all CS:GO Knives:
Click here.
List of all CS:GO Weapons:
Click here.[counterstrike.fandom.com]

To make things a bit more simple and easier. There is a website available that you can use to simply generate a code in a few seconds. You automaticly copy the command by hitting 'Copy command' button, go to your CS:GO and paste/enter the code into the console.

Simply click on this link: https://output.jsbin.com/gilusiw
If you are scared and think this link is fake, here is proof.

When you search on the internet you will probably see this Reddit post by Marximimus.
In this Reddit post is more information that might be interesting to read regarding this topic and for even more proof.

https://www.reddit.com/r/GlobalOffensive/comments/o940a6/you_can_use_the_recently_discovered_radio/

Apperantly you can also change colors.
For that, go to this link: https://pastebin.com/676MSdEc

If you insert a special character into the text, the rest of the message changes color. For example if you insert a character with ASCII code 15 (0x0F) the text after that character will be red.

For doing so you have to paste special characters in your message to make the part that comes after that character colored. However, this only works on community servers with sourcemod.

The special characters's hex id is '01' - '10'. (\x01 - \x10)
Here is more information regarding this: https://pastebin.com/pZvCnGaC

Source: Click here.

All CSGO Radio voicelines and objects
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2538495414

CS:GO Roles and description
Click here.
What is Trust Factor in CS:GO
Click here.
How to kick yourself in a CS:GO match
Click here.
Commands to all CS:GO knives
Click here.
CS:GO All the player/stats/information and history
Click here.