My P.S. Partner (2012)

After learning that his ex-girlfriend has a fabulous new boyfriend, Hyun Seung spends his nights wracked with insomnia and jealousy. Then one night, a phone call from a sexy stranger breathes new life into his gray existence. Even with her enviable looks and a successful boyfriend, Yun Jung feels love deprived. While attempting to spice up her relationship, Yun Jung resorts to giving her boyfriend a steamy phone call… only to find that the guy on the other end is someone else and she just can’t quit him!