Meghbela Broadband — Very low internet speed

Very low internet speed. I've taken a 60 mbps package but speed is very low. Facing problems during my zoom meeting mainly. speed test shows internet speed in between 10 to 20 Mbps download and 30 to 40 Mbps upload but very unstable. And also another thing in Speed test the optimal server is not the meghbele server why is that? and if I try to select meghbele Kolkata as a optimal server it not responding.