How to Repair Voicemail App?

At my last service refill (pagepluscellular, a Verizon sub)), my Galaxy S5 was reset and now the “built-in” VOICEMAIL App cannot connect to the voicemail server/service. I have to manually dial *86 to get my voicemail messages. Is there ANY way I can uninstall, shut down and restart the phone, then re-install the app to correct the apparent corruption of the original app?

I have followed EVERY troubleshooting step from Verizon (it is a Verizon phone), and tried to get help directly from pagepluscellular with NO joy to report. Total failure on all steps.

To be clear:

1) The ONLY means to get my voicemail messages is to MANUALLY dial *86 and I AM able to get my voicemail messages with this method

2) The built-in app CANNOT call/connect to the voicemail server.

3) My carrier says they have NOT disabled the app on my phone

4) pagepluscellular contracts with Verizon for all services and network services, including voicemail.

5) pagepluscellular did NOT deactivate voicemail on my account/service/phone