Website at signup got my address wrong, how do I change it?

When I signed up for Xfinity NOW, i selected my address, which is the 4th of a 4 unit building. However, my service address appears to have defaulted to unit 1 somehow. How do I change my service address? All 4 units have distinct numbered addresses, but when I signed up for internet I couldn't select one specific address, only all 4.