So some calls are not going through and are going to voicemail? It is possible that a 2.0 CDMA phone and a 3.0 GSM phone on two separate networks may have different coverage, there may be a local tower issue at the moment or the user may have had their volume down. We get a lot of tickets saying people are getting an error that says that the RW customer is not available not realizing that that is the default voicemail greeting if no custom greeting is recorded. When the caller is on WiFi but the phone is unreachable or on cell we forward the call to the carrier GSM or CDMA, like any other cell call on any other carrier.
There might not be anything to fix, it is still a mobile phone and signal strength may change as you move around and when the phone can’t be reached we send the calls to voicemail. We are like other carriers we just have more ways to reach the phone, but they are not limitless.