When people say it is still in trial it is been offered by BT sales, I was offered it yesterday not as part of a trial.
BT sales are renowned for offering to turn water into wine to get you to sign on the dotted line.
There are many threads in this forum complaining of promises being made during the sales process that can't be fulfilled in reality.
It is not unheard of for them to hear a service is coming in the future via an internal brief and then treat that as being available now.
If we give them the benefit of the doubt and assume it is being made available on a select basis, then you will need one of the BT mods to look into it for you because there is no information that I am aware of that can help you.
As far as I and others know (and have stated already), it isn't available yet as a service as it is still in trial.