Odd Sound Coming from my new Cassette
If it doesn't happen when you pedal ( and it wasn't like this before you took it to the shop ), it sounds like someone who worked on your bike at the shop managed to displace the plastic cassette guard that sits between the cassette on the spokes, or they somehow negatively affected the rear wheel hub. At any rate it, they didn't reassemble your bike properly. If I were you I would take it back to that shop right quick and make sure they fix it for you for free.