I got a phone call today from a company claiming to be calling me on behalf of Vodafone, and telling me my contract was about to expire and that I was due a "free" phone upgrade.
Alarm bells rang instantly as I vaguely remembered a news article about these companies, who are NOT affiliated to the mobile phone company they claim to represent. They offer you the free upgrade and say they will renew your contract, but it's actually bollocks - they tie you into all sorts of deals that cos you money and are VERY hard to get out of.
I rang Vodafone and double checked about my contract, which IS up for renewal, but they said to ignore anyone external, renewed my contract and I declined an upgrade. Sorted!
Just a warning to you all out there - always check with the phone company PERSONALLY than with a dodgy company!