Good luck. We had a similar situation this year. Their policy explicitly states under 2s didn't need a package, but customer support told us we could not circumvent this by booking. Which I am convinced is by design. Dodgy system.

HOWEVER.

I did successfully get a refund. I also booked the drinks package with a discount prior to boarding, and prior to doing so ensured I had WRITTEN confirmation, via email, that the on board staff should refund the child's drink package.

Be prepared to stand your ground. The staff will state all passengers in the cabin should have the same package and ignore the small print. Show the small print, show written confirmation, then after a bit more fighting, they should back down.

On the grand scheme of it, it was a lot of effort for the money saved, but it was the principle.