You might specifically have to ask for a 12 month contract as Virgin have just started implementing 18 month contracts. Actually this may be a change for the good as it means if you want to recontract it's only once every 18 months instead of once a year.
You could try the text messaging service.
Just send a text with a description of regrade to 07533 051809. Your message will go into a queue and a representative will respond to you as soon as possible. It may take a few days.
You can also call 150 from your Virgin landline, or 0345 454 1111, butbest to call at 8am to avoid call queues.
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali