"Many customers are locked into substantial contract terms attached to many phones, there must be robust reporting mechanisms and swift remedies so that customers can fix problems when changing provider is not an option," it stated.
The process of deciding what sites should be blocked needs to be more transparent and regularly reviewed, added ORG.
"There needs to be mechanisms that allow website owners to challenge a refusal to remove their site from a blocking system," it said.
"At the same time, there should be transparent reporting and mechanisms for problems, mistakes and resolutions."
In a further statement, Peter Bradwell, author of the ORG report, said: "The lessons for 'porn filter' proposals are clear. Default-on blocks can have significant harmful and unintended consequences for everybody's access to information.
"To help protect children online, the Government should reject 'default on' network filtering and work to give parents simpler choices and better, device-based tools."
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