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Fraudsters will impersonate everyone, from government employees to charities. Do online searches on persons or companies contacting you as well as products offered.
Ignore requests for money upfront or personal information unless from verified sources! Do not give these out to callers or respond to suspicious text and/or e-mails (credit and loan offers, job offers, "you've won a prize" e-mails).
Credit cards are more secure than wire transfers, reloadable cards and gift cards. It is impossible to get your money back from the latter and no respectable business or institution will ask you to use these for payment.
Be wary of free trial offers and always review your monthly statements for charges you don't recognize.