Virgin Media has apologised to some of its broadband customers after it mistakenly sent out an email saying they would all be getting "super-fast" connections.
The message was intended only for those who pay for the fastest internet connection, but was accidentally sent to all four million of its cable customers.
As part of the company's new pledge to increase broadband speeds, those currently receiving the top speed of 100Mb are to get 120Mb, while lower speeds will all at least double.
However, all its cable customers were told theirs would increase to 120Mb in the email sent out on Friday.
The company quickly sent out a second email to apologise for the error.
A Virgin Media spokesman said: "Following our announcement last week that we are doubling the broadband speeds our cable customers receive, we've started to write to let them know how it will work and what to expect.
"Our first email, intended for our 100Mb customers, was accidentally sent to some customers on other tiers which may have led to some confusion.
"We're sorry for any misunderstanding and will be writing to customers again soon to clarify how the upgrade will affect them.
"In the meantime, as part of our double-speed programme, we are delighted to confirm that 50Mb customers will actually be upgraded to 120Mb, meaning even more Virgin Media customers will be able to take advantage of the fastest broadband speeds in the UK."
The move to increase connection speeds is expected to cost the company £110 million this year alone and will take place from next month until the middle of next year.
It is in line with Government targets for 90% of British homes and businesses to have access to super-fast broadband by 2015.
Last October, BT announced it would be able to provide super-fast broadband for two-thirds of the UK by 2014, a year earlier than it previously predicted.
Virgin Media has said its new high-speed service will allow users to download a music album in less than five seconds and a high definition film in around five minutes.
It will also speed up the internet experience of households or offices which have several users connected at the same time.