I think you should try and spare a thought for the person who is being forced by the company they work for to use your first name. I work in a call centre and will lose my job if my recorded calls prove I am not usng the callers christian name. I find it terribly rude and forward myself and no matter how much we protest, management always knows better, doesn't it? I always feel extremely uncomfortable doing it but I have no choice. Maybe you should complain to a manager and not take it out on the person on the other end of the line.