This iOS app does basically the same thing as the above method. It starts a call, initiates a second call, then merges the two so it can be recorded. However, instead of calls being stored in your voicemail, they’re stored in the app. Automatic Call Recorder Pro costs $4.99.
Voicemail issues are apparently common across the range of iPhones. I have seen them from the older iPhone 5 all the way up to the iPhone XR. Sometimes it’s not the phone itself at fault, but the network that’s causing the problem. Sometimes it is the phone, and a few simple tricks can get voicemail working again.

We’re all familiar with this type of voicemail greeting. Simply put, a caller reaches you by dialing your number or extension directly. For an optimal personal voicemail greeting, be clear about who you are, the team you’re on, and when the caller can expect a callback. Unlike company and department voicemail greetings, you may not be able to configure a greeting for open and closed business hours. If that’s the case, use a general voicemail greeting that accommodates both scenarios.
Out of town? Your callers should know. Let them know with the following vacation voicemail greetings.