I phone 7

Update to iOS 13.4.1.

With the limited information that you have provided, I had to guess the problems faced by you. Some of it can be understood by reading below

Not available in many regions and countries --> Use Voice Control on your iPhone, iPad, or iPod touch - Apple ...

VoiceMail is a carrier Specific feature, ensure they have this enabled for you --> Set up Visual Voicemail on your iPhone - Apple Support

If you are unable make a call or receive; If you can't make or receive calls on your iPhone - Apple Support