Getting rank 3 in google is not that easy but they guarantee this to everyone so i dont thing it is true i think they follow some automated techniques which will bring you traffic in large amount in no time. Google wont accept it so better to go manual seo which will be helpful for your site in getting good rank in google.
I dont wanna cause a fight or anything but here is what I have to say. I think what rankpay really does is just spam your link around social networks like twitter and various spam blogs. At no stage has any genuine independant links appeared in the serps that they had placed for me. I think they are just simply employing either automated systems or indian freelancers to just spam links for you.
A client of mine received an automated spam from these guys today. Spamming for clients in SEO i ironic to begin with, since organic should provide them with plenty of leads (youd think). Second spamming suggest a need for quantity of new inquiries as in to replace a high churn of lost clients. BHW has a thread on these guys with results month to month from current clients. My first thought is that anyone that considers a website moving from $51 to #37 a success for 3 months work has clearly been working with the wrong people. The people you passed in position are often not even direct competitiors when you get do to page 4. Movement within the top 20 means something, but going from nowhere to slightly higher nowhere can be accomplished pretty easily by most anyone here in this forum ( I would hope)