Call costs
https://newsroom.bt.com/keeping-us-all-connected-at-a-critical-time/ https://www.bt.com/about/coronavirus/our-customers#accordion-vulnerable-customers
Note very carefully the words in bold…
To help our most vulnerable BT landline only customers, we’re removing out-of-bundle charges for the most critical services, such as UK landline and mobile calls, and placing a £5 per month cap so they can make the essential calls they need to keep in touch, without worrying about their bill.
There is also, of course, BT Basic which may help others: https://www.bt.com/help/landline/getting-set-up/help-people-with-impairments-or-with-particular-needs/how-do-i-find-out-more-about-bt-basic-