I bought a car and financed the roof rack, now know my model can't support roof rack. Is dealer in breach of c?

I emphasized that I needed roof rack for family vacations. Dealer ured it was no problem to install at the dealership and added it to the financing cost. At service they discover my basic model is not reinforced to support a roof rack. Now they want me to choose other options to make up the cost difference. Is this breach of contract? I don't want to finance sat.radio and premium carpet :o(