Take an old clean handkerchief with no lint on it, fold it and run the fold through the tension disks like you floss your teeth, there may be a residue from the last thread you used or lint. Check your instruction book as to how the thread should come off the spool before you thread the machine, I found on my new Brother it has to come forward a certain way. What size needle are you using? One that will let the thread flow easily through the eye or is it too small and catching the thread? If nothing else works and the one who serviced your machine doesn't like too far away, take it back and complain. He might have some suggestions about what thread and what size needle you should use.
Carol J.