Are you sure it was a 90 days free thing? I did the same thing last year but it was only when you bought it from Sony via the PS store that you got 90 days free.
There's no way a third party would be able to offer free time except by giving you a free 3 month code which you would have had to input separately.
There's no way a third party would be able to offer free time except by giving you a free 3 month code which you would have had to input separately.