How to correct voicemail timestamp

My voicemail timestamp for messages left is 3 hours behind. The time on my phone is correct. Ive called to ask how to fix twice. There was a network reset done and then i was given a short code then told to add the voicemail provider number at the end then pound and enter the correct time. I was also told to access my voicemail settings through the phone app which, for me, is greyed out so Im unable to make ant sort of change there.

Can anyone tell me how to correct the voicemail timestamp that hasnt been tried or been told to to. Ive tried restarting the phone and toggling the time on the phones time settings as well. ¡Gracias!