If this is the stair treads, it is possible your contractor added an anti-slip additive to the paint, this would make it feel like sandpaper.  For the walls it must have been the existing substrate (wall surface) that was rough or something in the paint. The only way to smooth it out is to sand down the existing paint to a smooth surface and add a new coat.  A clear coat can be added over top but this would do little too nothing for the roughness.