I renewed my subscription 2 days ago. As an existing virgin media customer it said my renewal price would be £25 but the invoice i have states that i have been charged £79.99.
Sorry for my reply.
How I can to understand - "Virgin / F-Secure renewal process and strange point with price-change" can be a popular trouble.
Under this community it was time to time noted (and probably under the Virgin Media community too) with same description (as your);
A lot of users did not back with result of situation (except meanings like: "all OK after the get support-talk" or "not OK" - if they do no get it);
Not sure about current situation - what if it was fixed already, but happened else one time...
So I think that most helpful step (at least - on current time) will be try to get F-Secure Support help directly.
It available with next options:
--> as phone-call:
--> as chat:
I not sure about useful/powerful status of this channels, but you able to try it.
And if it will be not helpful - maybe someone from official F-Secure Community Team will help you about getting support.