Slow internet speeds

And here I am once again needing to complain about slow internet! I have a 4mbps uncapped line with you and my download/upload speed is 0.48/0.28mbps!! This is NONSENSE!! I pay for 4mbps!!! Every time I phone support they say it has been fixed or they cannot see anything wrong, but doing a speed test reveals the above mentioned speeds! Opening websites takes more than 10 seconds to load, youtube videos keeps on buffering and it does the same on all my devices! I want someone to come out and fix this, because telephonic support does not work!