There is a plate on the bottom of the oil pan take it off maybe Your oil pick up is clogged ? There could be sluge in there ? You can see how bad or clean the engine is with a light .Your miles are low to have a worn out motor ,unless they never changed the oil.Oil level switch could be going bad also if the guys telling You to change the oil right after he changed it thats kinda bad iam betting the oil filter that was in there when he did it was in pieces and fell apart .