The best thing really would be to raise a fault at
https://faults.plus.net as others have suggested.
It takes you through a couple of things (changing the filter, trying in the test socket and an alternative router if you have one) to eliminate things internally that might be causing your disconnections.
If that doesn't sort your disconnections it will get it to the right team to investigate what is going on and begins running some checks on the line for us.
