Payment aggregators (aka third party processors) are service providers that allow other businesses to accept credit cards without having to set up a merchant account. They make money by taking a percentage of credit card sales and also a transaction charge.
Payment aggregators are a business on their own. They need to get approved for a merchant account to support their business to split up that merchant account to many businesses. It takes a deeper underwriting process, but they are supported and TRC-Parus does offer merchant accounts for payment aggregators.
Payment aggregators can provide some great services and you can investigate further on the differences between a merchant account and an aggregated account.