<p>The BT Sport app closed on 12th October and has been replaced by discovery+. <a href="https://community.bt.com/t5/TNT-Sports-on-TV-Online-player/The-BT-Sport-app-is-closing-on-12th-October/td-p/2312034">Find out more about activating TNT Sports on the discovery+ app</a>.
Now fixed for me and the person whose number I had (phoned to check and warning her that she might be billed for my calls). Of course it might not have been a simple swap. Will check my next bill for mistakes.