My bluetooth handsfree doesn't works anymore

Hi, I bought a sony x-plod MEX-BT4007U and pair my iPhone 4S with it, everything goes fine, I couldn't test the conectio because I had not have the speaker yet.

Now I install the speakers, reset the sony xplod and try to pair again, but didn't works, the only thing that pair is the MP3 function. The Handsfree don't.

I really don't know whats happand, in the first time works and now don't.

I already reset the xplod and redefine all the settings on my iPhone, but still nothing works.

I tested another cellphone (LG GT360) and it works!!! This old phone works the handsfree and the MP3 but the iPhone dont!

I don't know more what to do. If someone know what to do I will appriciate.

I thinking in restore to factory the iPhone, but I just wanna do that in last case.

Thanks