The time for asking people what they want and finding out what price they’d pay for it is not after the product/service has gone live, it’s before! As someone had mentioned earlier in the thread, you had the chance to collect thoughts on this already in another thread 2 months ago - Monzo Plus - Small Scale Trial.
Don’t get me wrong, you could easily change my perspective of Monzo Plus if you made it worthwhile down the line, but you shouldn’t be testing what works in a paid product after you’ve already asked people to pay for it.