2. Enter the destination you wish to transfer the call to, then press [SEND] softkey. 3. Once the receiving party answers, announce the call. 4. To complete the transfer, press again. If you hang up before the call rings, the transfer will fail and the call will be disconnected. Direct to Voicemail: Transfer a call directly to voicemail 1. Press . 2. If a phone rings once and then goes to voicemail or rings only briefly, it You can't definitively know the cause of a phone barely ringing and going to voicemail because neither a phone company nor the phone's operating system provider will tell you if your phone number is blocked.
On Android, a variety of apps can record a call directly, unless the phone manufacturer blocks it. On iPhone, recording phone calls is blocked, period. The apps that do exist to record a call—and there are quite a few—have a workaround, but it will usually cost you.

First, you need to turn OFF your WiFi if it is ON.Tap on the phone icon on your iPhone home screen.Press and hold 1 on your keypad to enter your voicemail settings.Enter your current voicemail password and set up your voicemail.Using the phone keypadHang up the setup and restart your phone.Go to your voicemail and check if you still see an error.Method 4: Reset Network Settings
Website: https://www.mightycall.com/blog/keep-things-concise-visual-voicemail-saves-time/