This book is a research work on telecom sector of Pakistan. it is a comparative study of two cellular companies Warid and Telenor Pakistan. After using a product user has a perception about the product and can express his opinion on others. These expressions are unpaid and unplanned and are known as informal sources. On the other hand formal paid and planned. These are advertisement, sales promotion etc.The main objective of this research is to find out the behavior of consumers when they come across formal and informal sources of communication, which source effects their buying behavior most positively or negatively.