Unhappy Noises Coming From My Phone?? Help?

I recently got the galaxy s5 and for some reason when my phone is sitting by itself it will make a noise as if I was calling someone. It's the tone you hear when you call a person and wait for them to answer and it will sound only once and do it again in about 5 to 10 minutes. I read around forums but they found that it was the NFC making their phone make strange noises. I turned NFC off and to no avail. Any ideas??