I assume you have watched the movie completely. There are different narratives in this film. One from Sameera and other what actually happened.
After Vinay Varma falls down due to Ashok's push, Ashok and Sameera both go down using a rope ladder. Sameera takes her phone out from her back pocket to call ambulance. But Ashok stops her from calling.
Sameera :Thank God he's alive. We have to call an ambulance.
*Ashok pushes phone in her hand*
Sameera : (*Yells*) What the hell Ashok!
Ashok : Are you crazy? If we take him to the hospital, we will go to jail.
Nonetheless, Sameera searches for her phone but picks up similar looking Vinay Varma's phone to call the ambulance. At 1:08:10 two phones are shown in the frame. Because she was tensed, she picks up Vinay Varma's phone.
It's later revealed in the climax it was the other way around. It's Sameera who pushed Vinay Varma.