Hotel industry

SirWe have a small guest house. With less than 20 lakh turnover less room rent of 1000 But we have tie up with on line company so necessary to enroled with gst so we are ready to enroll. But on line company charging us some percent as commission and 18. GST on that commission.is that Paid GST is refundable Can we charge diffrent rates for same rooms If we charge rent a room. For rs 1500=00. We charge GST @ 12 Another day we can charge for same room. 2200=oo If we paid GST on commission of company. It will be adjusted in input GST credit