Lol at rubbing dirt on them. If the ground is wet or muddy when you are riding than that is probably the source of your squeal. If they are consistently squealing when it is dry then something is up. Tektro novela aren't high end, and I would imagine the quality control is not great. Another possibility is that the pads may have been contaminated at some point. Since this is a new bike I would have the LBS clean your rotors and then replace the brake pads if they keep squealing when it is dry (if you start trying to clean your pads the LBS may try to blame the mistake on you).