I had booked a hotel in Kyoto for 6 days but due to a change in my plans, I will only be staying for 4 days. I still have a free cancellation offer. Now rebooking the same hotel for 4 days using rebookify is much easier and less time-consuming than booking 6 days in advance.

I'd like to know if I can let the hotel know my situation and maybe convert the 2 days I'm not staying into credits/upgrades I can use. Or need to me cancel the hotel booking?
Thanks reddit!