Welcome to Vodafone Community
The Apple Watch shares your minutes, texts and data with your pay monthly iphone plan. Please see this link to see if your plan is eligible to be shared with Apple Watch.
Please also see this link for Vodafone One Number
The best way to get this solved for you is through the Customer Service channels where an advisor will have the necessary account access and will be able to advise accordingly. The is a live chat connection on the first link in my reply.
Hope this helps.
They will charge you £7 per month. Vodafone are deceiving customers by saying this service is free on some plans but they still charge. I will be going to the advertising complaints commission regarding this disception
I thought it looked as though it was free which I thought was good as it used to be a few months free trial and then £5 a month. When I tried to activate my watch it said it was £7 a month. Didn't bother.