Cannot purchase z8 points.

Everytime I try to purchase z8 points I am getting this message:

"In order to deposit you must be at least level 21 in any of the RPG games or level 6 in Cross Fire.

Your account does not reach the minimum level requirement to make a deposit. Please come back later. Thanks."

But I am level 6 in Cross Fire already.
Can anyone help me?
I really want to get those z8 points, but I don't know how to solve this issue.

Thanks in advance.