Around 10,000 Sky customers are being told they will see their line rental prices hiked from 1 June.
Affected customers will see an 18% increase in their bills, with the price of line rental increasing from £12.25 to £14.50 per month.
However, the price hike is only for customers whose line rental wasn't upped in December last year, when millions were hit by the same increase (see the Sky to raise phone prices by 18% MSE news story).
Sky says this latest price increase is part of the same rise that hit most customers in December 2012, but due to the "individual circumstances with these customers' accounts" it couldn't notify them until now.
Affected customers can leave Sky without facing an early exit fee (see our Cheap Home Phones guide for help on switching line rental provider).
Customers facing this increase should receive a letter informing them of the changes.
Last September, Sky ended a price freeze, upping TV prices and call rates for millions of customers (see the Sky to raise TV prices and call rates MSE News story). It says there are no other planned price increases for its customers at present.
MoneySavingExpert.com's technology expert Becca Talbot says: "Customers who want to avoid the hike should look into paying for their line rental service upfront, in a one-off payment, as many can save by doing this."