"Gaga originally wrote "Telephone", with Rodney Jerkins, for Britney Spears. However, Spears' label rejected it and Gaga recorded the song as a collaboration with Beyoncé Knowles for The Fame Monster. Gaga said, "I wrote it for her a long time ago and she just didn't use it for her album. It's fine because I love the song and I get to perform it now." Additionally, the guest vocalist was originally going to be Spears, but for an unknown reason, Gaga made Knowles the featured vocalist instead." (Wikipedia)
Itt a Britney Spears demo:
http://v.youku.com/v_show/id_XMTcwMDk4Njcy.html