Hi Sheetal,
Training on Telephone Etiquette is really very simple as you know (may be).
Don't worry i am sure you will do well. Please find attached file on the subject.
After this topic you can try for
1) Communication Skills
2) Team Building
3) Time Management
4) Building Self Confidence
5) Attitude towards Work
6) How to get rid of Stress or Stress Management
7) Keeping Positive Attitude

Presentation Skills
9) Leadership skills
Also try to get relevant feedback after the training, by preparing proper questionnaire & ask the trainees if they want training on any specific topic.
Regards
Sapana