Hello, I am from Argentina. Will this site allow me to contact an inmate through a letter ? And if so I would like to know what kind of payment ways you have?

A good percentage of the InmateAid members are international (see testimonials). It's easier and less expensive to use this service versus the international postage (not to mention the amount of time it takes to get there). The website uses Stripe as a payment gateway and they take all types of payment.