How can I reset my mobile Xfinity voicemail to the standard greeting?

Hi!

I want to reset my mobile voice mailbox back to the standard greeting. The Mailbox menu is very limited for me. 
Only options I have is listen to voicemails and personal options. Under personal options I can only re-record a greeting. No other options available.

I read, that a reset or reprovisioning of my voicemail is necessary. How can do that?

Thanks,

Patrick