Not providing what they promise

I've been a Mweb customer for many years now. Lately and after many calls made to the technical people, the speed of my line (40/20) from the middle of the month and specially on the last week if the month, drops to an average of 30/12 or even lower in the evenings. Opposite to what they say, I do not by a minute agree that the speed is not throttled towards the end of the month. My access to TV via the Internet has becomed a daily frustrating buffering.