iPhone mailbox says it’s full. But it’s not

I tried all the recommendations, and nothing works. I have an empty mailbox, but continue to get the message that it’s full. I also tried the suggestion to go to settings and change my mailbox pin, and my phone says I can not change my pin, my mailbox is not accessible. Besides calling Verizon, are there any other suggestions? I don’t have hours to sit on hold with Verizon