You counter them by revealing the physics behind it and relying on one of the reputable Speed Calculators such as http://www.kitz.co.uk/adsl/max_speed_calc.php
I did so with Orange when they got uppity and got my way
. Mind you I had to formally write to them; "Tech" Support had no inkling of the technical aspects of BB.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC