There would be a £25 non fault call out charge (it used to be £99) to do the work you require.
You should call 150 from a Virgin landline or mobile, or 0345 454 1111, option 2 (Faults)
When calling Faults you will hear the automated response asking you to press 1 for the link to online support etc
Ignore all the options and don't press any buttons then you should be placed into a queue and an agent should pick up the phone and book the tech for you.
Or wait a day or two and a member of the Forum Team should pick this up for you and arrange a tech visit.