BT customers with landline-only packages will see their monthly phone bills cut by £7 from Sunday April 1st.
Monthly line rental fees will be reduced from £18.99 to £11.99, a reduction of 37 per cent, which works out to a saving of £84 a year.
BT will also cap line rental and call charges, to increase by no more than inflation, for three years.
The move comes in the wake of a review by Ofcom, which noted that telephone line rental prices have gone up in recent years, despite wholesale costs falling.
The watchdog therefore concluded that landline-only customers have not been getting good value for money, compared with those who buy landlines bundled with other services, such as broadband.
This discount will apply to BT landline customers who do not buy broadband from any provider, which means up to 900,000 people will benefit from the changes.
BT has confirmed that the vast majority of customers will not have to do anything to receive the discount, as it will appear on their next bill automatically, while it has written to a group of customers to clarify if they are eligible for the reduced rate.
Jonathan Oxley, Competition Group Director at Ofcom, said: “We had serious concerns about soaring bills for loyal landline customers. This was hurting people who rely on their landline, many of whom are elderly."
Indeed, figures from the watchdog showed that 66 per cent of landline-only purchasers are aged over 65.
As a result, Mr Oxley believes the cut in prices will ensure these customers get "a fairer deal", as well as protection from price rises in the coming years.
Commenting on the changes, BT said: "We welcome the fact that up to 900,000 of our customers who don’t have broadband will receive a substantial reduction in the price of their line rental.
"We listened to our landline-only customers and made a voluntary agreement with Ofcom to reduce the price of line rental for them by £7 a month."
Richard Neudegg, Head of Regulation at uSwitch, added that this is "welcome news" for BT's landline-only customers.
"BT volunteered to implement the cut for these customers without broadband at a rate sitting at the upper end of Ofcom's proposal, which is laudable given landline-only services are typically taken by more vulnerable - particularly elderly - customers," he said.
Mr Neudegg went on to note that landline-only customers have "lost out" in recent years, as the shift in competition in fixed telecoms has led to voice-only services being overlooked in favour of broadband.
However, he stated that many of these people regard their landline as a "lifeline", which makes the implementation of this price cut "all the more welcome".