Any company that allows the creation of an online account through their website must have an option to delete these accounts clearly available.
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It is very easy to sign up for account for shops etc. online but many do not give the facility to delete the account directly from their website. Occasionally it can be done through a web chat but often it requires emailing the company and often the email address is not easy to find. It should be as easy to delete an account as it is to create one.