BrummyGit
Whilst I have sympathy with your plight I would like to point out that Virgin Atlantic's terms and conditions are clearly laid out on their website. I know on good authority that call centre staff do not have the means to "decide prices in their heads"; the fares displayed on thier screens reflect the seat prices available at that time and these, believe me, can change by the minute. The staff do not have the authority to override this.
My best advice to you would be to email their customer relations department; they are a friendly bunch and Virgin prides itself on its customer service. Travel with them this time and I feel sure you will not want to go elsewhere.