After I published my last post, one of my ex-colleague pointed me that "the thing" I was assuming to be a speaker/microphone, is actually a Sim Card Slot and I just need to push it and it will eject out automatically.
It turned out that he was right, except that there's no eject or pop out mechanism in place, so you actually have to insert a thin pin in to the hole, tilt the pin a little to create a lock and then try to drag it out.
Finally this issue was resolved. Or I think it was...
The next problem was that the Sim Card Tray has two slots, one was the standard micro sim slot but the other was not and seems like a memory card slot. I tried different ways of placing the second sim but it didn't fit into the slot.
So now I'm thinking to reach out to a technician and have my second sim trimmed down to the shape of second slot and then try using both sims with this phone. The phone's OS (Android) clearly indicates that it supports 2 Sims, but why they have a non standard Sim card slot, is something I'm unable to understand. And, if the second one is not a sim card slot, then where to insert the second sim card?