Did the dealer cancel the GT line s you had on order?
The manufacturer deals with Mb and both decide what is coming to the scheme, not the dealership. Have you spoke to Mb to see if they excepted the 4 trim. My fear is if the GT line s you ordered has been cancelled and Mb don’t allow you to have the 4. Which is doubtful because the 4 trim I believe is no longer made or on Kia’s order books.
The only way a 4 trim would come through but doubtful, is if it was a customer order when it was in production and got cancelled by the customer. Even then he may have promised it to you but sold it on retail.
A typical salesman full of bull sh!t by the sounds of it.
My advice ring Mb and clarify whats going on asap 🙂