Many consumers still struggle to get out of unwanted subscriptions such as gym memberships and online streaming services, according to Citizens Advice.
Analysis of almost 600 problems reported to the service found that in just three months consumers paid an average of £160 on unwanted services.
Sometimes, consumers misunderstood terms and conditions, while some companies made cancellation difficult.
The head of the consumer group, Gillian Guy, said firms must "act responsibly".
"Subscriptions are very easy to sign up to but can be difficult for consumers to get out of. We know people are wasting time and energy trying to cancel subscriptions while paying out of pocket," she said.
Companies refused cancellations by asking for more notice – stretching to six months in some cases – or told people they needed to cancel through a specific route, such as phone or email.
CA said one person who contacted the service said they tried to cancel a subscription after they were made redundant, and were asked for proof from their employer – including a P45.
Most payments are thought to be through a Continuous Payment Authority, where companies can change the date or amount of a payment without giving advanced notice.
Frequently, consumers said they felt it was unclear they were being signed up to a recurring payment or that the contract may continue on an auto renewal basis.
Under the Consumer Rights Act 2015, businesses can't enforce terms on consumers that are unfair.
CA's report marks the start of National Consumer Week
CA's need-to-know tips about subscriptions:
- Always check cancellation rights
- Be aware that there is a cooling off period, usually 14 days
- Follow the cancellation policy, or you could be liable for missed payments
- Challenge unfair terms & conditions with the firm or its trade body
- It this fails, go to Trading Standards and/or Citizens Advice
Consumer Minister Margot James said the UK's consumer protection regime is one of the strongest in the world, but there was always more to do.
She said: "With 40 million people in the UK now subscribing to at least one product or service, this campaign from Citizens Advice will help ensure consumers can shop with confidence and know what their rights are should things go wrong."
Leon Livermore, chief executive of the Chartered Trading Standards Institute said consumers should remember that if an offer "sounds too good to be true, it generally is".
He added: "We're also eagerly awaiting the government's upcoming green paper that sets out their vision for consumer protection in a post-Brexit landscape.
"We will continue to work actively with our partners… to build a safer future for UK consumers."