I have an S4 that was replaced by AT&T over the summer. I have the phone paired to my toyota camry and highlander. Each time, I am able to make one call using bluetooth, than for some reason I can't use it after that. I can make and receive phone calls but no one can hear me and I can't hear them. I have to reboot the phone before I was able to make and receive phone calls. I called samsung several times but this is the second device with this issue. I really don't want to go back the iphone and pay a lot of money for it. Samsung wants me to send it back for a repair, but why don't they fix this issue with a firmware update. I am just a little annoyed by the whole situation. Please help me!!!