I think the issue you are having with NatWest is because they are treating this as a continuous payments authority for a subscription that you legitimately took out rather than fraud, which is what it is looking like. It will just be the ordinary banking team that would deal with cancelling a continous payments authority. You will need to speak to the fraud team.
The legislation on continuous payments authorities has changed because they were notoriously very difficult to cancel. You now have the legal right to insist the bank cancels the payments. I would be asking for a refund dating back to the first time that you contacted them about this. If they don't deal with this, you can take it to the financial ombudsman.
https://www.fca.org.uk/news/news-stories/continuous-payment-authorities-it-your-right-cancel
However, it does look like this might be fraud.
If you've ruled out that there are no subscriptions on your DH or DD's app, potential explanations that aren't fraud are:
Did your DH or DD previously have Uber using a different email address/Uber account and delete it because they weren't using it, then signed up again with a different email account? Uber Eats and Uber Rides used to be separate apps so many people had separate accounts. Also, there were issues when they combined the apps. I had to create a new account because I got stranded having taken an Uber to an event but couldn't get one home because of technical issues with the new app 😂It's possible that your DH couldn't get the new version to work and set up a new account. He may have been signed up to a free subscription on the old account that is now paid for or the old account could have been hacked.
As a PP suggested, has you DH ever paid for Uber on someone else's account? The cards are listed as Visa, Amex etc with the last 4 digits. It is quite easy to mistakenly select a card of the same type without checking the numbers if you've forgotten that someone else's card is saved to your account... I have also had this issue with Deliveroo randomly charging tips to someone else's card that was used on my account because of a technical glitch with the app autofilling a different card from the card used to place the order.
Or it could be fraud - either someone else is using your card on their Uber account or, as a PP suggested, scammers can set up an account to make a transaction appear to be from Uber. I suspect, if NatWest think this is just a continuous payments authority cancellation rather than fraud, they won't have investigated if the payment is genuinely to Uber.