3 sims 1 ex-Virgin 2 old 02 Questions

Hi. I have Virgin home broadband with the Volt data doubling deal in place. This is because I also have mobile phones with 02. I want to keep the Volt BB benefit.

I have two 02 accounts (one has always been an 02 account; one was a Virgin Mobile account which is now 02). My ex-Virgin 02 account benefits from Volt data doubling.

How can I check which of my O2 accounts generates the home BB Volt doubling?

I'm considering ditching one of the my two 02 mobile accounts but don't want to lose my BB Volt benefits.

TIA