Hi AWD123
Have you tried via the My O2 app?. Or using the website? https://accounts.o2.co.uk/
Once you're in the app, go to 'Offers', then 'Supercharge your world with Volt', then tap 'See what you can get. From here, simply fill in the details you're asked for and within 14 days you should have your benefits applied on both your O2 and Virgin Media accounts.
If your broadband and mobile accounts are in different names, or the names don’t match (eg Chris and Christopher), you’ll need to activate your Volt benefits in My O2, and they’ll be applied within 14 days.
You'll also need make sure the address on your O2 account matches the address on the Virgin Media broadband account, whether it’s in your name or someone else in your household. If they don’t quite match, you can edit your address in My O2.