Microphone not working

I have a 2 alienware laptop's and the microphone's for these laptops dont work. I am running window's 10 have tried troubleshooting many time's but no use. Cant believe my friend has a very cheap laptop and he never encounter's any problem's. To make thing's worse when I try to get some online help from dell, there online agent requested me to pay 400 dollar's for there service's.