Hellphone (2009)

To surprise her daughter on her birthday, a mother saves up and buys a second-hand cellphone. But before she can get home, accident befalls her and she ends up dead. The phone was stolen by a janitor who was trying to make ends meet. His excitement over the phone is cut short when strange things started happening. He along with his friend team up to uncover the truth behind the unusual phone and the mysterious voice that keeps on calling.

Unfortunately the movie Hellphone is not yet available on HBO Max.