Thanks for posting and a warm welcome to the community.
My apologies that you are experiencing slow broadband speeds. I know how frustrating this can be.
As -tony- mentioned the Modem SNR (signal to noise ratio) for downstream is too low and for this I can arrange an engineer appointment for you. I've sent you a PM (purple envelope icon, right corner) with some details for you to confirm please. Once you have replied I can go ahead with the appointment.