People in Guernsey are failing to take up a service which blocks unwanted phone calls, according to the island's data protection service.
The Telephone Preference Service allows people to register their number so it is not used for cold calling.
The amount of people subscribing to the service has grown from under 200 in July to nearly 300 by the end of September.
But the Data Protection Office says more islanders could benefit.
Dr Peter Harris, Data Protection Commissioner, said: "Fundamentally, it's a lack of publicity.
"We've had lots of calls complaining about marketing calls and also silent calls, which are very unnerving particularly for older people.
"They can register with the database free of charge and that should reduce this nuisance."
Mr Harris also said local businesses marketing to the British Isles should screen their call lists through the service, which is operated by the Direct Marketing Association.
Marketing firms are legally obliged to check the list, and make sure they do not call any numbers on it.
Companies calling numbers which have requested no calls can be fined.