Budget insurance want to pay my car according to old model of my car

I have bought my Mercedes c 43 facelift 2018 December 23 and insured it with budget insurance and I took it for assessment . I got involved in an accident they took my cat to assessment of which it was written off. Now budget Insurence want to settle my car for less than it’s value and they have been sending me from wall to wall to a point now they are telling me about recordings when I took the police simple because they want to rob me the true value of the car and they want me to settle for the value of the old model of my car