My parents got visit visa. They were sending the application through mail. The travel agent who helped them for this,just now clled them and told,the visa has been approved for 3 months(They requested for only 3 months) and it started on July 7th and they have to leave USA before October 6th. Anybody heard anything like this?

As you should know that visa is an application to enter in the United States at the Port of Entry. Your parents will have to arrive in USA by October 6. It does not mean that they will have to leave US on October 6. The period of stay in USA will be determined by Immigration Officer at the Port of Entry. It could be between 3 months or 6 months. Good Luck.

Persons over a certain age (60), who fulfil other conditions for Visa, need not appear for visit visa for interview. In certain cases, Visa officers may call them for interview.
Good luck.