Garg ji and Samir ji,
I did not jump in earlier for the obvious fact that I am very bad with these look-a-like Convolvulaceae members !!!
Yet to tell you frankly, when I saw for the first time, the photos of Samir -- the first thought was I. triloba.
I double-checked the leaves, the buds and the flower, however the description ... leaves entire or ** somewhat 3-lobed **, base usually cordate, kept me from commenting here.
In simple words, no thoughts here about ID.
Samir ji, if possible to visit the site again, get to these flowers before they lose their prime, and capture side profile of the flower, preferably a close shot, showing the throat as well as sepals ... those may help us all in getting close to ID.
If no chance, it is better not to believe it as I. triloba even if it tempts any of us !!