New rules which make it easier for broadband customers to change supplier came into force today.
Ofcom drew up the regulations because a "significant minority" of people had problems switching. The telecoms regulator will monitor broadband firms and take action against those which do not comply.
Under the new rules, suppliers must give customers a numeric code when they want to move. Some people had problems switching because their suppliers would not hand out the Migration Authorisation Codes (MACs).
Others had trouble changing supplier when they moved house because the previous resident was still registered to their phone line.
An Ofcom spokesman said: "Most consumers who want to switch their provider do so without a problem, but Ofcom is aware that it can be very frustrating for consumers who have had trouble moving between suppliers or moving house."