Yes, I have exactly the same issue. THREE times now I cave called BT to say BTSport keeps saying my details are incorrect. The first time the guy was frankly insulting, blaming me!
No one at BT can resolve this but we've had NO problems for the past 3 years! Nothing has changed, except we're now all paying a LOT more! If this continues for another week I am going to demand a refund, because I can't even cancel!
I'd not MY PROBLEM, it's BT's!