I have a problem with purchasing in a game it is called rules of survival and i cant buy any diamonds from it i just want to ask help please?

If you haven't already contacted iTunes Support as instructed to do by the message that you are getting you should do so (we are fellow users, these are user forums, we can't help you) :

- 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'

Help me..i want buy diamonds rules of survival

Help you with what ? If you are getting a message to contact iTunes Support we can't help you, you have to contact iTunes Support