We are using OTRS 3.1 for a while now and it works great

We have only a slight problem with escalations. When an phone call outbound is attached to the ticket it gets deescalated. But when an agent attaches an phone call inbound this doesn't happen.
ofcourse it should no longer escalate when the customer is updated on his state.
I cannot find what defines deescalation/unescalation behavior Anybody any idea?
Thanks in advance