it happens a lot on my home as well but i dont see any change in speeds. as far as speedtest goes i never trust speedtest.net as they have "priority/peering" based speed tests. again im not defending Jio here but you cant get 100% of "advertised" speeds all over the world or even "nearest server". Speed test is really a grey area of the ISP .... there is no right way or correct way to test your internet speeds, all rated ISP speeds are only liable to "their node". All i can say is make a complaint and wait it out for issue to be resolved, it is most likely be routing issue or they maybe upgrading hardware on their end or some pipe might be disconnected and they would have to reroute through different pipe which is already running at its full capacity which coupled with additional traffic might slow you down.