How can I play a voicemail on an old iPhone?

I have an old iPhone (iPhone 4) and I'm trying to play an old voicemail that is on the phone. It is not saved in my voice mailbox. For example, if I call my voice mail box, it is not there or saved, but it is on the phone itself. The voicemail is over 6 years old, but it is still on the phone. However, it won't let me play the voicemail. Will I need to temporarily activate this phone to play/record the message?

Apple is known to degrade their phones over time so people are forced to buy new ones

The voicemails are usually in the realm of the carrier, not the phone. Though the iPhone may list it as being there I suspect it is actually long gone.

Either way though I'd suggest checking with your carrier about if it could still be there or not.

Your phone only has a pointer to the voicemail as it stood six years ago, and hasn't had the chance to get an update since the day you disconnected it. That pointer will disappear when it gets back online.

If the original still exists at all you would be able to hear it on your current phone.