Welcome to Vodafone Community
Firstly I would like to apologies for your post being missed.
From what you have said it does sound like there could be an issue with the SIM not updating on the network properly through the iPad.
Firstly can I ask if there is anyone who has an iPhone that you could place your SIM into and connect to the internet?
This would update the network on the SIM and has been know to resolve the issue in the past.
If this doesn’t resolve the issue then I would look at getting a new SIM from your local Vodafone Store as it sounds like this could be the cause on the problem that you have.
Please give this a go and let me know how you get on.