Regarding internship related issues what to do

Hii sir I was awarded summer internship for the period of 2 months in the month of May this year and I also received office letter regarding that from the concerned authority but the office letter did not contain the date of joining for the internship. The concerned authorities there always told them that they need some time to do some of the arrangements.After some days they stopped taking my calls and stopped replying for my messages and I waited for them to reply for the first month and then I accepted my fate. I also received internship from some other company during the period and due to this delhi company I didn't accepted their offer because that internship was in Ranchi. So please tell me how can I legally tell them that they did the wrong thing?