Index Function to search from a range

Hi,
I humbly seek help and tips to get my Index Function fine tuned as it does not return correctly. I have two sheets, Sheet1 consists of Company Name and Person In charge. Sheet2 is a full list detailing specific person in charge in a specific company. I need sheet1 Column B to be updated automatically when Column A is entered. Attached is the file for your easy understanding. Any help is greatly appreciated.