If they are on you go to the chat box and click the ( I think ) orange box that says clan and you should be able to talk to them from there even if they aren't on zomg and it works too if they aren't in your area.
i recently was trying to send a big PM/ message to all members in my guild. But it says i can only send to multiple members if they are my friends. Is there any way to send a message to everyone in your guild? please pm me the answer.