HeySiri Not Working

I try to set up HeySiri but it isn't working probably because there is some problem in the mic on ios 10.3.3.

Even when I make a video call on whatsapp the mic isn't working.

I faced the same problem back on ios 9.3.3 on my iPhone 5s and currently I'm facing the same problem on my iPhone SE on ios 10.3.3.

Note: This is a software problem and not a problem with Whatsapp or Siri in particularly.

I even did a hard reset many times but the problem still pertains.

I don't want to update to ios 11 so, please fix this issue asap as I'm really irritated with this mic problem.