Naturals Unisex Salon — not giving bill and refuse card payment

Address: Thiruvananthapuram, Kerala, 695583

We went to salon near infosys, kulathoor, thiruvananthapuram, kerala. There they are not ready to accept card payment and don't even bother to give bill for the service. We payed around 3700/- (Facial, hair spa, half arm wax, and eye brow). Later we had some confusion about the amount we payed and we went back to ask bill. But the were not ready to give the bill saying that the is some problem with the software and they cannot give bill.
We are paying 18% extra amount from the brochure in the name of gst and the guys are not accepting card payment and not even ready to give bill. From this what we need to understand. The mistake happened from our side was we asked the bill after the payment.