poor and unreliable internet speeds

I have been a subscriber of the unshaped unlimited 20mbit download 2 mbit upload package for some time. I cancelled DSTV and opted for Netflix as a better alternative once moving onto fibre, unfortunately due to unreliable download speeds this has proven to be frustrating experience as I regularly have to wait for buffering in the middle of streaming some program. On complaining to Home-Connect they get me switch off the router etc. which helps for a bit, but reverts back to sub-standard speed. I have consequently cancelled the subscription.