From the speeds you quote it sounds mode like FTTC not FTTP - fibre to the cabinet and then your normal copper line from cabinet to your home
can you post hub stats if hh6 then advanced settings then technical log information
can you enter your phone number and post results remember delete number https://www.btwholesale.com/includes/adsl/main.html
check line for noise. Dial 17070 option 2 should be quiet and best done with corded phone
are you using test socket with with a filter to see if that improves your connection
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