Techavera Solutions - Substandard coaching classes refusing refund

I reached out to Techavera as a working professional looking for GATE coaching in Statistics (ST) on weekends; Techavera advertise themselves as providing coaching for all kinds of competitive exams as well as professional courses.
*. I was told before making payment worth Rs. **,*** that I would get a refund if I don't like the teaching faculty. However I was given a 'non-refundable' receipt thereafter. Wary of this inconsistency, I got them to explicitly mention a refund clause on the receipt.
*. I was utterly disappointed in my class with the appointed teacher as he turned out to be a mechanical engineer who had no idea about statistics. When he confessed to not knowing much of the ST portion we discontinued the class. Right after that I asked for refund, but the Techavera people begged me to give them another chance; so I let them arrange for another teacher for next weekend based on the clause that I should get a refund if I am not satisfied.
*. The next teacher was a MSc Statistics qualified person but had no idea about GATE questions. A couple of similar teachers followed and I was left guiding the institute on how to screen the teachers before sending them to teach!
*. I told them finally that I would like to discontinue because this is not working out for me. Upon their constant insistence for more and more chances I told them that I would not be appearing for GATE anymore because it seems like a very impractical option for me given the kind of help (quality of teachers) available. Now they completely changed their stance and refused to initiate the refund saying that it's non-refundable as mentioned on the receipt; they gave me one of two choices - to keep trying out different teachers until a good one is found, or to take up online lectures if I'm not willing to travel for classes.

I am left feeling appalled at the state of such coaching centers, not only taking the students' time for granted but in fact looting money under false promises. They also had a couple of women talk to me who spoke disrespectfully and ridiculed my reasons for discontinuing while clearly stating that I should have thought about these things before giving them my money! I also offered them to keep *% of the fee for their efforts over these ** days and give me back the rest, but they refused.

Overall, I want to discontinue their services because I no longer have the willingness to prepare for GATE. I am willing to reimburse them for going through the effort of trying out * to * teachers, but it must be noted that only * lectures have taken place till date and nearly none of the exam portion has been covered; there should be no problem in making the reimbursement as it is no loss to their business which works on the aggregator model - connecting teachers with students on a lecture to lecture basis.