WARNING!
You may only activate it only if you never had Play Station Plus before
A credit card is required to redeem your PlayStation Plus trial, but you will receive this trial without charge. Unless you cancel your subscription at least one day prior to the end of the 30-day trial, your trial will automatically convert to a 3-month PlayStation Plus subscription, and will automatically be deducted from your PlayStation wallet according to the PlayStation Network Terms of Service and User Agreement. This 3-month subscription will continue and automatically renew until you cancel it.
You may cancel your subscription via the account management on your PSN account or by contacting customer support.