unable to set up voicemail iPhone 7

Voicemail is a carrier function. Your carrier probably needs to reset your voicemail. Force closed the voicemail part of the phone app, then contact the carrier. They can reset your voicemail, and then you should be able to continue. Make sure they have your account provisioned for Visual Voicemail.

force restart iPhone, hold down the down volume key and the sleep/wake button as the same time to force restart.

Forced restart took me back to square one. I began setup again, and the same thing happened. I did this several times. This doesn't solve the problem.