An option with far fewer cables is the RecorderGear PR200. It records your conversation via Bluetooth. The call button in the middle of the device can answer calls on the Bluetooth-connected phone. Hold the PR200 up to your head to talk and listen, as if it's the phone. It also features a USB end to quickly access recordings on the computer. It will hold about 144 hours of conversation before it fills up the 4GB of storage. It also records like any digital recorder sans smartphone, since it has an external pin-hole microphone.
Go to your phone Settings and open Cellular option. Now tap on the toggle for Cellular Data option. Turning on the Cellular data; Try using your voicemail and see if the problem still exists. Method 3: Setup Your Visual Voicemail. If you are unable to set up your voicemail through phone settings, then you can try setting it up through your carrier.

Open Phone → Make sure you are on Keypad → Press and hold the number 1 for a few seconds. It will call your voicemail; You can check your voicemails here. 3. Force close and reopen the Phone app. To force close Phone, on iPhone X and later swipe up until you see the apps in task view, then swipe up again on Phone.
Call Recorder Lite also uses the make a call, merge a second call technique. This free download requires in-app purchases in order to listen to more than the first 60 seconds of your calls, though.