Hello Sandip,
The Gillingham Exchange which you are connected to shows a capacity for 5.5meg which suggests one of two things,
Either the supplier’s servers/connection is causing as issue or your equipment is throttling the signal.
The best thing you can do is report to there technical support and follow everything they ask you to do to the letter and if nothing changes then bite the bullet and change suppliers.
When calling them ensure you are connected to the master socket in the house with all other sockets unplugged and the micro filters have been swapped, this what they will ask you to do so at least you can be a step ahead.
Kind Regards,
Michael.