Dear Chaitali,
This kind of situations have been in practising in the recent past. Further, i would like to give some suggestions and at the same time, I would also like to know what is the radius of your hiring. I mean, do you consider candidates within the state or from any states in India?
Coming along with my experience, I can suggest you these things:
1. Some peope are good in expressing themselves in writing but they fail in communicating face to face..... same way, many people convince thru telephone but fail to do so in personal interviews.
2. Take an initial interview on telephone: do not give appointment for that. You will get most of your information when you actually discuss on things, not just letting the candidate speak. Put open-ended questions.
3. No matter how far you will fooled on telephone, always ensure to take the candidate through a personal face to face interview with HR and respective department leads as the final rounds before selecting.
4. If you have been in practice of delivering appointment letters, a letter of intent will do stating that subject to final apperance interviews.
5. Try to cross question the candidates on their personal details in the resume, family, education, past experience, etc. The most you confuse the best you will get out of the candidate.
6. When you feel that you are being fooled, try to take the references i.e. their past and present company numbers.
7. As other members said in this forum, SKYPE has become official and already in practice for video interviews. So, propose this to your bosses. They will appreciate it.
At last, if the candidate was refered by your company employee ... you can understand that the candidate knows about your practices and recruitment process.
Good Luck!