To be able to qualify for a product review, you have to first purchase the product and use it, it's not possible to review what you haven't use, even though I understand other people use bad reviews on their competitors products page just to steer customers to their own products, it rarely works.
Buy the product or service and have experience on what it feels like to use it and then you have earned the right to have a say on what you feel, how the service was delivered, your perception of it, that's the best way to review products.