This IS genuinely Vodafone. They don't ask for whole security code as stated in another comment, Just two digits, For security. They easily pulled up details of my account and a linked account that only they would know, Without me giving any other details. They look to see if they can save you money by putting you onto Unlimited data plan for small amount each month on top of your tariff. Genuine call
Called saying they were from Vodafone and wanted to check if I was paying too much on bills and look for better deal. Not sure why Vodafone would offer that - only 12 months into a 24 month contract... Why would they highlight to me they think I’m paying too much with them?! Phishing scam I think.
They saying they calling from Vodafone and saying they would like to see if they can help reduce my bill. Asking for my security code I said I couldn't rember then he wanted to know the email address I used. I hung up as it didn't seem right