iphone 4s not detecting bluetooth headset

Hi all. i have a iphone 4s ios 7.1.2 which i recently erased and set up as a new iphone. I have a Plantronics M50 bluetooth headset (just bought 2 weeks ago), and when i try to connect my iphone to it, it will not even detect the headset. I have a nexus 5 and it the M50 connected to that so i know it works. I searched in google and a link to this forum came up in which the user had similar issue with the same headset. Their iphone, i think, detected the headset. I have read the troubleshooting article and have done some steps on that. I have erased all network settings. I did NOT erase my iphone and restore it since i recently set it up as new. Pls let me know if anything can be done. I don't think anything is wrong with the headset since it connected to another phone. Please help.

I really don't want to restore my phone again since doing so will result it installing ios 8 and i don't want to do that. any help is appreciated.