Sabrina Carpenter's not a fan of yodeling ... or what she thought was yodeling -- expressing an opinion that's getting her into a bit of trouble online. The pop star brought down the house at Coachella Friday ... and, one excited fan showed their appreciation with a high-pitched trill in between songs that rubbed Carpenter the wrong way. Check out the clip ... Carpenter's sitting at a piano, about to play "We Almost Broke Up Again Last Night" -- when the call draws her attention, and she bluntly tells a fan she doesn't like it.