I took the hint from Vijayasankar ji and searched the site flowersofIndia- can it be Jacquemontia pentanthos ?
Flowers and leaves resemble to the plant I shot - only confusion is the size of the flowers. As per the site, size is 2.5 cm dia, but to me it was smaller.
Tanay ji, It is not Ipomoea indica- I think. The leaves are different ( not 3 lobed) and the flowers are not of funnel shaped. Also the size is smaller and the colour do not change at different time of the day.
Please confirm the id.