I call my wife's Koodo iphone 4s when the phone is beside me not being used, the call goes immediately to voice mail. I hang up and call the Koodo iphone immediately and the phone rings properly. This has been happening regularly for the last few weeks. My wife is a visitng nurse and uses her phone to receive calls from patients. The phone is always on. It appears the network can not find the phone initially, is there something we can do make sure important calls are not missed.