How the 7-day free trial works
Pro is free for 7 days, then £3.99 a month unless you cancel. The first charge date is shown before you start, you get a reminder 2 days before it, and you can cancel any time from Account → Settings → Subscription.
A card is needed to start the trial, but nothing is charged during it.
Two days before the trial ends you get a reminder in the app (and by email), with the date and the amount.
There is one free trial per person, account and card.