Poor Fibre Internet Speed

Poor client service and poor fibre network. We are being ****** by this company. Previously i was on 15/15 mbps and always struggled with the download speed. Now i changed to a higher internet speed of 50 mbps download and 25 upload, the download speed is always half when i check internet speed test. I have addressed this through emails bt i am not being taken seriously. I can't watch 4k content because of such.