As a process of elimination can U try ure Sim in another phone to rule out either the Sim or Phone which may be at fault.
If it's the sim speak to Vodaphone about a sim swap.
http://m.vodafone.co.uk/mobile/simswap/index.htmDoes this happen in one place or everywhere?
If one place check your masts via
https://www.vodafone.co.uk/our-network-and-coverage/uk-coverage-map/Where did you get the phone from ? As occasionally a permanent 'No Service' in the phones status bar can mean it's been imei barred by the Network. Their Customer Services will be able to clarify.
Current Phone >
Samsung Galaxy s²⁴ Ultra 512gb.