Hi
You need to transfer your mobile number and tariff from the micro sim from your previous phone to the nano sim for the iPhone. This is called a sim swap.
The SIM cards are account specific I believe so you need a contract one if on contract and a payg one if on pay as you go.
Any vodaphone store can supply the correct nano sim and perform the sim swap In house or if you have the correct sim then follow
http://m.vodafone.co.uk/mobile/simswap/index.htmUsually completed in minutes but can take up to 24 hours.
Once the service stops on your old SIM card place the nano sim in your iPhone ,and keep turning airplane mode on and off or turn the iPhone off and on to help re connection.
Current Phone >
Samsung Galaxy s²⁴ Ultra 512gb.