Delayed or no voicemail messages

I have an iphone SE. For the last couple of weeks, messages are not delivered for several days, nor do I receive a notificaiton that I have a message. Today, someone called and when I didn't answer they were not able to leave a message. I tried powering off and resetting my network settings. My husband has an iphone 11 and he is having similar issues. Our zipcode is 55391. Please help.