Bought land from Land Developer, Now No access to my land.

I bought land from a land developer. Now I have no access to my land. At the time of purchase, the land developer said, Once we acquire all surrounding lands, we get approval and make a plot and sell. After years, they developed the area and got approval. but they did not buy in between land to connect our land to new developed plots. Now he sold all plots. even construction done. Now we have no access to our land. Backside to our land, Kendra Vihar residential projects are there. (Central Government). They build Pharse 1, 2, 3. So the Kendra Vihar outsource private builder asked our land for rental. To keep construction materials and sheds for workers. They have been using our land for more than 5 years for rental. We asked Way for the above landowner for road access, but he is not responding. It is possible to get access through the Kendra Vihar entrance. (Central Government). or we apply legally above the landowner for road access. Our seller is not taking our calls. The person who did all documents is our relative. She just told me it was an investment. Once they start the project, we sell to them, and we buy good property. but we cheated by our relatives. please advice me to sort out the issue.