I landed at a class C (KAVL) without switching to tower from approach. I don't think they were training controllers that day but the same two controllers were o

I landed at a class C (KAVL) without switching to tower from approach. I don't think they were training controllers that day but the same two controllers were on both freqs... rolled off and sent my call "off at echo" and got a nice "traffic calling approach say again". Didn't get the dreaded number to call on the air since they knew the school... filed a NASA report and nothing else came of it. mistakes happen. Related, on a check ride with the chief instructor while a controller was training he absolutely chewed the controller out on the air for giving me an immediate turn instruction at ~350' AGL. I don't think that was called for and it made me feel horrible and made the rest of the flight awkward. But from that day on I was much more comfortable with a simple "unable" when I got weird requests.