Anthem, K0739, and modifiers

I recently received a denial in which Anthem is asking for a modifier on the labor code K0739 when replacing parts on a power wheelchair K0823. This is the first time I have ran into this problem. They keep telling me that i have to have the patient contact their employer to find out the information i am needed but this is next to impossible as the patient never answers their phone. Can someone please help? Thanks.