BT is targeting customers who it says are regularly breaking their monthly broadband download limits.
BT offers a range of broadband packages
The telecoms company has sent letters to more than 3,000 customers it has identified as excessive users.
They will be given the choice to pay for their high use or risk losing their connection altogether.
The company will not say how many people have already been cut off, but said they were downloading between 100 and 200 gigabytes per month.
BT offers a range of different packages with monthly download limits of between two and 40GB.
Their guidelines say they will not take any action against people who occasionally exceed the monthly usage.
However, for those that regularly go over their limits, BT says it will contact the customer to suggest a product more suitable to their needs.
The telecoms giant said that the number of customers it has sent letters to represents a very small proportion of BT broadband users.
It defended its actions, saying that it has to buy bandwidth.
"If a small percentage of users are using far in excess of others, it distorts the amount of bandwidth we have to buy, which increases the costs for everyone".
Andrew Craig of Web User magazine says that 100 to 200GB a month was excessive for a personal user.
"These are generally people who are constantly downloading and uploading movies on file-sharing websites," he told the BBC.
There are now more than 10 million broadband connections in the UK, according to telecoms watchdog Ofcom.