How do I increase voicemail volume (iPhone 13 Mini)?

Thank you for your reply. However, I mentioned in the message that the volume is already at max volume, i.e., the volume up button on the left side of the phone is at max volume and can't go any higher. I have seen the same complaints but I have not seen a resolution. One reply was to return the device within the warranty period. But mine is over 2 years already. Maybe Apple engineers can offer a solution for us suffering the same issue? Thank you.

Thank you, Lawrence, for your reply. I have not tried to hold the volume button while listening to the voicemail. I will give it a try the next time. I hardly get voicemail because I screen the calls. Thank you for mentioning the cellular carrier. I will call Bell when I have a voicemail the next time so they can listen to it. Thanks again for your time answering my question, greatly appreciated.