Voicemails not showing up from days ago

We check our voice mail thorughout the day and right before closing. It will tell us we have not messages. Then the next day we will check it and it will tell us we have a message from days ago. It happened today. It showed a message on the phone and when we checked it was from last friday when the customer left the message. This is something that can cause an issue due to them thinking we are not calling them back.