BT has denied allegations that it plans to give an inferior service to thousands of heavy Internet users.
According to documents leaked to the BBC's Watchdog programme, some 34,000 customers of BTopenworld Anytime - BT's 24/7 unmetered narrowband service - are being migrated to different dial-up numbers.
Punters are being assured that the move is designed to spread the load and improve the overall service - which costs £14.99 a month - for users.
However, insiders told the BBC consumer affairs show that it was likely that these customers would get an inferior service.
An insider told the BBC: "We're effectively being told to deny that the service has changed. The customer is paying for a service and that service is being altered - I think to their detriment."
The TV show also cited a leaked document which claims that the monster telco expects consumers "to get the engaged tone" when they try and dial-in to the new numbers.
According to Register reporter, Kieren McCarthy, who is a BTopenworld Anytime user and migrated to the new number last week: "I have noticed a marked deterioration in the service since then. I was told the move would improve my service."
However, BTopenworld has strenuously denied the allegations and said that it has no plans to offer a two-tier service.
"All customers, regardless of which number they access the service with, continue to receive the same BTopenworld Anytime service, at the same price, with the same terms and conditions. We are not seeking to disadvantage any customers or move them to another service," it said in a statement.
In August BTinternet warned some 400 extremely heavy users that unless they curtailed their online activities they would be booted off the service. While some users have heeded BT's first warning, around 270 users had failed to respond to the telco's request and were sent another warning earlier this month. ®