Incomplete service and lack of communication

I bought a car at Nissan with the help of Stefan he served me well the problem occurs where in few days after buying a car the airbag light on the passenger side shows a warning I took it to the dealer ship they took out the part that was a problem I have been running up and down for that part to be replaced but no luck I try to talk to Stefan no luck please assist me with my car I had hope that Nissan as a world known dealer ship that I trusted my queries will be solved but no it's a stressful end where my safety is not taken to consideration by Nissan