Why I can’t buy diamond from rules of survival?

Somebody on here might be able to help you if you say what the problem is. Why can't you buy items, what happens ? If you are getting an error message what does it say ? If you are getting a message to contact iTunes Support have you done so ?

Your screenshot tells you what you have to do i.e. contact iTunes Support. If, for some reason, you haven't done as instructed you should do so (these are user forums) :

- go to http://www.apple.com/support/itunes/ww

- click on your country's flag (the country where you are, and which is therefore the country on your account)

- click on Contact Support towards the top right

- click on Get Help under 'Talk To Us'