The background music of the mobile phone endorsed by Song Hye Kyo is "I Got a Cold in That Corner". This song is the demo version of "Guardian Angel". The singer of this song is Hong Kong female singer Feng Xiyu.

The original singer of "Guardian Angel" is Deng Jianhong, from the album "Only Talking About Love, Not Saying Love".

"I Got a Cold in That Corner" is a song with a very strange name, which comes from a special record called "Only Talking About Love, Not Saying Love".