Welcome to Vodafone Community
I understand your viewpoint on this.
Could be worth using Live Chat or customer service on 191 and speak to Retentions to see what can be achieved although there may not be as good deals with an Apple iPhone flagship phone that's just been launched @rchiileea
Also can depend whether the contract is at an early upgrade stage or end of contractual term stage.
Current Phone >
Samsung Z Fold³ 5G.
Previous Phone >
Samsung Note 20 Ultra 5G - SM9860.
Looking at the screenshots @rchiileea the logged in plan has unlimited data access built around the plan you are currently using and the not logged in plan has 25GB data access.
All customers pay the same price new and existing, if you don't need unlimited data, Vodafone should be able to offer the same with 25GB data.
It's always worth looking at third party deals, these are often cheaper. It's simple enough to move the number to the third party deal, if you use the forum search facility you will find examples of how this is easily done.