The first strategy to avoid paying an erroneous bill is to verify all bills or statements right when they are handed to you. For bills paid with a credit card, the card holder should check the amount of the purchase. This should not be seen as questioning the honesty of the store clerk.�
Errors tend to occur in payments carried out automatically through a bank. Consumers should examine every debit recorded in their account and stop at each one that smacks of irregularity. Once the account-holder is certain there is a problem, he or she should document it in order to file a complaint. In most cases, consumers' gripes vanish with a simple call to the customer service number of the company that made the mistake. All major companies have their customers' movements computerised and can check them in real time. So it may just take a telephone call to clear up the situation and correct any error or inconvenience that has been caused. If this does not happen, the consumer must turn to the department responsible for the alleged error and provide copies of documents, receipts or bills that back up their case. Collecting evidence is not always an easy job because with some services there is no meter in the house that records whether the billed amount reflects that amount consumed. Files claimed over electricity, water or natural gas have a good chance of holding up because meters don't lie.

Legislation defending consumers
Before filing suit -after checking with a lawyer- consumers can report the irregularity to consumer affairs departments of their local government.

Law 26/84 for Defending Consumer Rights says governments have the obligation to guarantee the defence of consumers and users of services, and regulates in a detailed fashion the following issues:

-The role of consumer associations in defending and representing the rights and interests of consumers

-It �specifies the benefits of seeking justice through a consumer association.�

-It specifies which ways of conflict-resolution are available to consumers.

-It protects consumers from risks that affect their health or safety;

-It protects their legitimate economic and social interests

-It requires indemnisation or reparations for damages

-It requires correct information about goods and services, training and education of consumers

-It requires hearings and participation in the devising of general norms for defending consumers' interests through consumer associations

-It calls for legal, administrative and technical protection in cases of inferiority, subordination or defencelessness.