I doubt if any ISP would dare. See
BT SIN 498 section 2.2.1:-
Note : It is the DLM system that sets the line profile, and this should not be interfered with by CPs/users setting rates, SNR margins etc. at the modem.
(CP is the Openreach name for ISPs. CP = Communications Provider).
My broadband basic info/help site -
www.robertos.me.uk. Domains, site and mail hosting -
Tsohost.
Connection - Three 4G, tbb tests normally 35-45Mpbs down, 65Mbps off-peak, 9-24 up.
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If you never think of anything off the wall, you'll never think of anything original.