Talk to Pediatrician on Cough With Mucus In Chest And Runny Nose

My son 3 years of age having cough from last 8 days with runny nose.i go to a doctor and he give me the syrup kafcool and sait that it is a common cold but after 4 days of giving medicine there is no relief so i changed the doctor told him the previous medicine and he gave torex syrup with Linzim suspension but after giving 2 days of these medicine there is no relief in cough or runny nose.kindly explain what is good in this situation is it viral infection common cold or bacterial infection or suggest some medicine