Hi Lakshmi,
It is very difficult to understand the problem without knowing what kind of connection you are using, but it seems that there are a huge amount of packet losses taking place in you transmission processes, this maybe due to several reasons such as a cable fault, or inferior quality switches, or maybe if u r using VoIP then this problem is sure to crop-up, u need to check you connectivity, insure that there are not too many telecom carriers involved in carrying a call that is generated either overseas or inland. Any thing else u would like to know?
Regards
Amit