I have spent the last 2 days trying to enable the greyed out 5G SA switch also with very little help from Vodafone so ended up researching it myself. I had a lightly different problem, in that I am already using an eSIM. I found from a Vodafone partner website they had all the reasons why it couldn’t be enabled and the problem comes down to both physical Sims and eSIMs and when they were issued.
SIM Card Compatibility – If you’re still using a physical SIM that was issued before April 2022 or an eSIM issued before January 2024, you’ll need to replace it with a new SIM that supports 5G Ultra.
So in my case I had to follow the physical Sim swap process, even though I am using an eSIM, in the Vodafone account under settings, manage and physical sim swap which took a few minutes to complete and this issued a brand new eSIM and problem solved, 5G SA switch enabled and 5G Ultra working on my iPhone 16.
I hope this helps anyone.
