I have an IPKII+NEC Dterm 80 that has been installed for several years. Some days ago, the voice mail doesn't work. Then, I called a tech to fix for me. He just cancelled the greeting and voice mail, and suggested me to change a new one. Now, when I use my cell phone to call this IPKII, NEC Dterm 80 will not ring until I heard 5 rings from my cell phone. Anyone know what happened?