[otrs] Reply to a customer ticket

Hello! I have upgraded from OTRS 2.4.x to 3.0.6. Until today we were testing the ITSM features of OTRS::ITSM, which works great. Today, we began to test the ticketing features, so we could fully migrate from our old ReadyDesk system to OTRS. However, we cannot find a reply feature in the ticket display. When I zoom to a ticket, there is a <select> box with -Reply- in it, but nothing happens whatever I do with it. Am I missing, or forgot to turn on something? Thanks in advance! Gergely Polonkai