O2 broadband customers could see bills rise by as much as £4.12 at the end of March.
Loyal O2 broadband customers are set for another round of price increases next month as package costs go up by as much as 27%.
The provider upped its costs at the start of the year, in line with the new 20% VAT rate, but now prices are set to go up again - with loyal customers the hardest hit.
From 1 April, customers on the legacy Premium package will pay £13 a month instead of the £10.21 they pay today - an increase of 27%. Other customers will see a rise of between 14% and 24% depending on their package - with O2's newest customers facing the smallest increases.
A spokeswoman for O2, said: "In September last year we refreshed our broadband packages to reflect how customers use the internet. We want our customers to continue to receive a great service, which means investing more in our network and, as a result, we are increasing our prices.
"Customers on our packages launched in September will see a small increase of between 14p and 58p a month from their first bill on or after 31 March," she explained. "For those on our older packages the increases are higher but they can move to one of our new packages, where the increase will be considerably smaller.
"Customers who receive our Access package will see increases of between £2.63 and £4.12 a month." O2 Access is offered to customers living outside of the provider's own network and who receive their broadband over the BT network instead.
She added: "We appreciate there is never a good time to increase prices, but we believe that our award-winning packages offer a great experience and value for money."
O2 was known for its generous fair usage policies, but last year it revamped its packages, cutting download allowances to as little as 20GB a month for Basics customers and applying a more rigorous fair usage and traffic management system to its All Rounder and Works deals.
The provider still offers a high standard of service though, with fast, reliable broadband speeds and discounts for existing O2 mobile customers.