Why dose my earpiece in my 640XL go off often?

[Windows Central Question]

Earpiece in my 640XL goes off often.

hi
i'm from India & I'm using a Lumia 640xl for last 6 months. on the very first day with lumia I noticed that the earpiece was not working during calls but i was able to complete my calls using the loudspeaker & am experiencing the same problem now n then. pls suggest wt to do. is it a hardware defect or software conflict...