how to turn off visual voicemail

That's not entirely true. When contacting the carrier, they stated that they are unable to turn this feature off on their end because Apple has not provided them with a means to do it.

swarner wrote:

I don't like visual voicemail and want to turn it off on my iphone 10.

There is no settings to turn off visual voicemail.

IF you wish to no longer have that feature, then you need to contact your cell phone provider and let them know. Only they can disable it off your phone.