Mate, I'm also from Shillong. BSNL FTTH is working fine for me. 100 Mbps+ for both download/upload at night.
Day time performance = shit because TechDyrect the LCO in Shillong only has 1 Gbps uplink to their OLT number 1 and 2. There are approximately 600 customers split between the two OLTs. Obviously 1 Gbps uplink is a joke. That's not enough to handle 10 customers on 100 Mbps plan.
If you live near BSNL exchange, chances are you are taking the fibre directly from BSNL. Go to NIB and tell them to check your port profile.
Also avoid using the crap
ONT they give you, it's probably from a brand nobody ever heard of. Put it in bridge mode and use your own
router to establish PPPoE connection. Use CAT7 LAN Cable to get rid of bottlenecks.