I feel cheated!!!

******* of an ISP! I ordered a 50mbs line and I'm only get 4mbs at most! All my videos keep buffering as a result and movies stop playing every other minute. I done several speed tests and none of them reach anywhere near 5mbs and yet I'm supposedly on a 50mbs Fibre line. This is unacceptable and unfair! I'm basically being cheated and made to pay for something I'm not receiving! I'm changing to another ISP immediately!