Unfulfilled promises of speed

My wife was a customer with the 400 mbps  and everything was fine , I canceled This plan and started my own with 1 gig plan but since day one I am only getting about 350 Mbps , after replacing the router and many customer support and tech support calls , no body has been able to the fix the issue , I even had two tech visits , and even  I high tier private tech come and  reported that the issue was with the node. but Xfinity keeps blaming clay electric and fpl for the issue , but in the mean time I am still paying for a gig . This is illegal and shameful that Xfinity is unwilling to budge and provide a higher plan for  free for those that they know they can’t receive  the promised speed and now I can’t go back because the $40 of 400 Mbps is no longer available  instead they are charging more but only for  the 300 Mbps plan , what else can I do other than report the issue to the fcc and the district state attorney for possible fraudulent and illegal business activities ?