In order to change the character's name you need to write the command

/changename

For example:

/changename TestName - change the character's name to TestName

You will see a confirmation window

The name can be changed no more than once every 24 hours.

The cost of changing the name is 1000 Wcoin.

After changing your name, it will be announced in global chat that you have changed your name to a new one.