Unfortunately you have no choice but to accept it. The acceptable sync speed range for your line is 80-62meg as shown on the DSL checker screenshot you posted earlier. This would have also been provided to you when you took our your contact with BT and at the time you were obviously happy to accept the terms, including the acceptable range of speeds.
You're within that range, therefore your line is working as expected and BT, nor any other ISP would investigate a speed problem.
I may as well get Virgin Media 200Mb unlimited FTTH. £24 a year cheaper than BT over x 2 the speed & no copper wiring issues caused by sloppy engineers.