Customers using Vodafone's 'Dongle' for mobile broadband access have complained about slow download speeds and blocked websites.
On the Vodafone eForum, a number of users have bemoaned the fact that they have been unable to access websites including Facebook and Amazon and are instead being met with a domain name system (DNS) error message and a blank screen.
One user wrote: "I've had this Vodafone mobile connect lite and already it's doing my head in! When I try to log into Facebook I get the DNS error message."
The Vodafone dongle is a USB device that provides users with broadband internet access wherever there is mobile phone coverage and costs £15 a month on an 18-month contract for a data allowance capped at 3GB.
Following the complaints, Vodafone asked members of the forum to supply examples of the error in an attempt resolve the problem. Initially Vodafone posted a number of solutions on the forum but these were later removed.
"Previously we posted a walkthrough of how to temporarily change your DNS. It's come to our attention that this no longer works either, so the eForum Team has endeavoured to find you an alternative solution," Vodafone explained to forum users.
According to a Vodafone spokesperson the problems are caused by a "network issue" and a fix was "being rolled out across the network".
She added the number of users affected was a "minority" and that refunds or credits would be given on a case-by-case basis.