Any communication before, during and/or after the deals are closed are carried out in the Overgear chat. You can open it at any time in the lower right corner of your display, or by pressing "Contact Seller" in the order details.
Any other means of communication (apart from the in-game chat, if it's necessary for order delivery) are forbidden. Violating this rule inflicts fining. Any arrangements made in the chat have the same power as conditions listed in the order details. In case a debate appears, arbitration guarantees to study the communication between the Parties. Any profanity is forbidden and blocked by special filters.