Negligence by private diagnostic lab

I got my blood sample tested for dengue at a private diagnostic laboratory. They claimed to provide the report in a couple of hours. I got the report after 52 hours.(Their report mentions the sample collection time and the time when report was printed). I learnt they had sent the sample to Delhi (around 9 hours of distance from my place by road) as their lab didn't have the related infrastructure to carry out the test. I wonder why didn't they just inform me and advise me to visit some other lab. This would have saved a lot of precious time required for medical attention. Instead, they said they would deliver the test report in 3 hours ( obviously a false statement and obviously they knew it's not possible as the sample was to be sent so far away). The main part, the report was +ve, i.e. dengue was detected. In the mean time I had started self medication so I guess I prevented the situation from turning really dangerous but I really wonder what could have happened if I was left waiting for the report. On the top of it, the lab guys were so unapologetic and said it happens often so it's okay. I want to prevent this from happening to any other person. Please suggest the legal course of action.