Cashify — Unsatisfactory repair

I booked a repair service at Cashify. They were supposed to do the repair in three days. When I didn't get any update after three days, I approached the customer care service. They said that it would take another three days, but I didn't get any update even after that. Finally, after 15 days, when I asked them to return my phone without repair, they promised that the phone would be delivered to me without repair. But the very next day, they repaired the phone without my consent and returned it. Afterward, the phone stopped working within a week. When I reach out to them, they are asking me to pay again for the repair. Because the repair was done without my consent, I want them to return the repair cost. Any help in this regard would be highly appreciated.