The new PocketSurfer2R (£199) comes with an option to buy unlimited lifetime data usage for a one-off £59.99.
Manufacturer Datawind says the device - which comes with an embedded 3G SIM - is now the most cost-effective way to access the web via the mobile network.
In addition to the new 'Immortal Plan', owners will have the option to buy unlimited usage beyond the first free 20 hours at £5.99 per month.
PocketSurfer2R comes with a full-colour widescreen display, a backlit QWERTY keyboard and touchpad.
The device includes a built-in GPS receiver and location-based services.
Suneet Singh Tuli, CEO of DataWind, said: “Unlimited usage will appeal to many of our users who find the PocketSurfer so indispensible that they regularly access it dozens of hours per week. Lifetime usage will also appeal to those who have bought PocketSurfer as a gift, whereby they can ensure that their loved ones don’t have to ever again pay for using the internet in the UK."