"Flaming Katy" and "Florist Kalanchoe" are common names for Kalanchoe blossfeldiana.
Calandiva is a registered trademark for a particular series and I agree that your pretty plant is not Calandiva Yellow since that one has double blooms.
If your wasn't labeled at the time you acquired it, I'm not sure if you can know an exact cultivar name but you can enlarge your image in the database, scroll down to the bottom and submit a proposal to move it to the species
Florist Kalanchoe (Kalanchoe blossfeldiana), or submit a proposal to move it to the general database entry for all Kalanchoe
Kalanchoes (Kalanchoe)
