Log into your BT account on the website and Log a Fault (in the link from the Footer of the website).
I'd the same problem. You'll find it'll probably NOT be the hub's fault but the card at your local Exchange. Get a BT Openreach engineer to check your line and card at the exchange first.
Before you phone 151 can you try factory reset by pressing the recessed button on back and holding 20/30secs until lights flash
remember to turn off smart setup
You didn't post if you checked it is not line noise causing your line to drop connection
dial 17070 option 2 should be silent and best with corded phone
if no noise then phone 150 and see if you can get replacement hub. Should be free if you are still in fixed term contract