job presentation!!!

[I.P.]

Hi there, Doctor!

I am currently preparing for a presentation to get a new job.
I had another 2 interviews that went ok, and now I have been told to prepare a presentation for 30 minutes. The topic is ambigous - "about sales", I have to choose. This will be the first problem
This company is in telecommunications and I applied for a trainer position (training on the procedures and products, not sales for the moment).
For the moment I am a call center trainer (I train the new employees in call center) in a cosmetics multinational company. I don't know much about sales...and I don't have such a great experience with presentations. What I do now is not such a great deal concerning presentations.
I would really need some advices since I find this site very interesting and usefull!
Well... if anyone can tell from their own experience, I am open to any ideas...and I am kind of desperate
Thank you all anyway and wish you all success!!!!
I.P.