I am on the Fibre with Halo broadband package. I also have a 5-SIM family package. Since lockdown all five of us (3 secondary school children and two adults working from home) have hardly touched our data - we rely on our WiFi for our mobile phones. But since lockdown we have continued to pay the same fixed charge for our mobile data. Will BT show good faith with us and apply a rebate to our Mobile Phone bill?
No, they provide you with what you ordered, some months you might not use it all, there's no rebate for doing so, no mobile company will do that.
You can login at www.bt.com/mybt and regrade your package, downgrade if needed, upgrade later, the family sim plan will renew for 12 months but 4 of the 5 sims will remain on a rolling 30 day contract.
As @-Richie- said no mobile company gives you a refund is you do not use all your data in the month but some like SKY allow your data to rollover and accumulate for 3 years