"Voicemail box full" even though all messages deleted

This question has been asked previously, and the answer that was deemed "correct" was to contact your cellular carrier. I just spent over an hour with my Verizon support who attempted a full array of strategies to no avail. Verizon's recommended solution was to use the Verizon phone app plus the Verizon account app, which was not acceptable to me. Through this process, however, I discovered the culprit that was filling up my voice mailbox: even though I <thought> had deleted all my voicemails, the voicemails from BLOCKED CALLERS were still on the phone in a separate page. Replicating the process for deleting the voicemails from blocked callers is challenging, as the menu options are not visible if there are no voicemails in the section; so these instructions may need tweaking: Open the “Phone” app on the iPhone. Tap on the “Voicemail” tab in the Phone app. Scroll all the way down to the very bottom of the voicemail list and tap on “BlockedMessages” voicemail inbox. Once there, you can either delete individual messages, or select the Delete All option at the top right of the screen. You do NOT need to go through your local carrier to remedy this situation.