Plusnet is offering a discount for 18 months worth £143.64 on its Unlimited Broadband & Phone Line package.
Subscribers can pay £20 a month (plus £6.99 in set-up costs) to receive speeds of up to 17Mbps and unlimited downloads.
Consumers will also receive a landline connection from which they can make free calls to other Plusnet subscribers, as well as enjoy round-the-clock access to the firm's customer support.
The promotion comes after Plusnet launched its Plusnet Mobile service on November 29th last year.
Customers can pick from a wide range of tariffs, which the firm says will combine great prices with generous data, minutes and text bundles.
Commenting on the move, Plusnet said its new mobile offering builds on its ongoing commitment to offering "great value deals" to customers, without compromising on top-quality service.