Well keep in mind that 95% of the people that are there are nice. It's the calls they get that piss them off...If you are rude, they will be rude right back. They were very helpful to me when I had problems with the Zune software, partially because I had a cool head and minded my p's and q's, even though I was extremely upset at the matter.
If you wish to speak to a supervisor, then say so. There is no number for that. Just call back, and try again. If you feel that they are rude, ask very nicely to speak to a supervisor.
Proud owner of a Zune HD 32GB
Halo 3 30GB
2 Zune v1 30GB