How to hold a private coaching institute responsible for lack of knowledge on course being taught

I have joined a institute by name GATE -IIT, Bangalore for PLAB 1 course. Before joining I was promised and explained by the GATE IIT, that the whole session for PLAB will be completed by February of 2021 and I will be in a position to give the PLAB exam in MARCH. Over the course of 6 months I have attended the classes directly online and also via the recordings provided. I have felt the coaching to be not in tune with the overall PLAB curriculum which I have expressed to them multiple times. By the end of year, Out of 32 topics that needed to be covered for the PLAB exam, only 5-6 were taken. There was no information about the rest of the classes. The management seemed to be ignorant about the total number of subjects to be taught for the PLAB 1 exam.  In my opinion, the classes taken were more in line towards the USMLE curriculum than PLAB and I felt the institute was not oriented with PLAB exam. Moreover, limited test materials and notes were provided despite multiple requests.  I have realized  coaching in GATE IIT is not going to help me in giving PLAB exam. This was brought to notice to the coordinator. I had expressed my dissatisfaction with the tutoring and asked for a refund. Despite multiple messages and requests,  my messages on WhatsApp were not replied and were not attended to. When I expressed my dissatisfaction and request for refund in the USMLE/PLAB/NEET group, I was removed from the group without notice. After multiple attempts, they have refunded 30000 out of 85000 that was paid by me. More than 15 members are affected by this . The management is behaving arrogantly and has blocked all our numbers and prevented us from messaging them over whataspp or message. Can you tell me what can be done for this ?