Aquaguard Total Ro — its not working properly

Sir I purchased a Eureka Forbes Aqua guard Total RO. The exact price is 14500(INR).When their service person came to install, e carried the unit with him. We didn't look or examine the unit in their shop. We purchased that and leave that in their shop (Coz they told us that theirs service person will carry it and install it the next day).The next day the service man carry the unit. and started to install it. But my doubt is that we exactly don't know what was in the box like what parts were there in the box exactly, were in there the genuine parts. We noticed on the installation day the service man open the unit cartoon box in front o[censored]s but we noticed that the 'Main Filter' of the "Aqua guard Total RO" was in outside from the unit not inside the unit. It came separately from the unit. When we asked him to open the unit he opened that we noticed there, one filter was not fitted inside that means there’s only four filter and one side is blank ( where's 5 filters have must should be there inside ).we asked him about that he told us that, the main filter comes separately from the unit. we took his voice with confusing mind. He installed that. But we still don't know the main filter he fitted ( Which was carried/came separately ) is that the genuine filter or any other ordinary filter. Sir please give us some ideas how we recognise the filter And what parts exactly come inside with the unit.( One another doubt comes from that they took from us 14000 rupees instead of 14500 rupees from the exact price of the unit. If they can is OK. But question is that reducing 500.00 rupees and insert another membranes (ordinary filter in the unit).What exactly actually.