Full Coverage Insurance- they say they wont cover wheel damage

I was driving to work and hit a badly repaired pothole/sink hole. I was going 30mph and popped my tire and severely damaged the rim. I made a claim with my ins. company. I just bought my infiniti from a dealership 5 months ago with not stock rims/wheels. They are another brand, not infiniti. My insurance company called me back and stated they will inspect the wheel but if it is not infiniti brand it will not be covered and I will have to pay the difference in price between the wheel i had on my car and the inifiniti. Is this correct or are they trying to not cover something they should. The car has everything on it as it was when i bought if from the dealership and put insurance on it the day before i drove it off the lot. therefor it was insured as it was. Please let me know if this is in fact true that they dont have to cover the wheel because it is not infiniti brand even though i didnt buy it like that.