Didn't find anything after a cursory search. What is the best way to contact a hotel in advance of a stay about an existing reservation? I couldn't find any contact info except a phone on the hotel page of the Marriott website. Is calling the best way to go? Or can they give me the email address of the front desk manager? This is for the Residence Inn Philadelphia.

I have a points reservation for their standard room (king plus sofa bed) and want to upgrade using either points or paying cash for a double queen plus sofa bed since there will be three of us--me, my son and my mom. This is an option for a paid room but not for a points reservation for my dates, at least not using the website. Is Marriott like Starwood where you can call the main reservation number and use extra points for a better room? Or is this up to the individual hotel?