@Compuaccord the info @iniltous and @licquorice have provided is correct. You can't be charged for a call that you didn't dial. Pressing a number on an incoming call from a potential scammer is not recommended but if you do it won't result in BT billing you for that call.
Thanks
Neil
Thanks for the confirmation @NeilO
Moderators are all BT staff.
@Compuaccord wrote:
Thanks for that, we can try and beat them at their own game now.
I wouldn't recommend it, never good to poke a hornets nest.