Entirely your choice of course, but you would get the same response from any ISP.
If your cooling off 14 days has passed then you will have cancellation fees to pay
I actually registered on this forum just to come and search for the solution to my problem.
Which is near enough the same as yours, but I am not complaining. I certainly would NOT be phoning BT. They have provided me with the service and it works, I'm happy with it.
It was my problem I wanted to change the firmware in an old router I had :-) therefore, my issue, which I will fix. You are getting the service you are paying for, no need to cancel, not their fault!
Leaving bad feedback is a little bit petty, your are the sort of customer BT could do without.
Ah well, enough said, I'm off!