Any reason why its BT Infinity 2, Infinity 1 is cheaper and will give the same speeds.
Retail might listen for 10 seconds and then say its above the minimum so its fine.
Retail might give you option to leave or stay. Leaving gains you nothing as will be same speed elsewhere.
No legal obligation on anyone to provide you the retail advertised speed, just platitudes explaining the range of speeds.
NOTE: Do the neighbours actually have a running service? Or is the they are better based on the estimates?