I'm trying to do correct the Voicemail number on my iPhone 6 plus?

I'm trying to do correct the Voicemail number on my iPhone 6 plus?

Oh are you? That's wonderful! Let me know how it goes. This is next:-
Hi. I'm man in my 50s. Many years ago, when I was in my 20s, I often didn't feel like walking over to my washroom during the night even though it was attached to my own bedroom. Private bathroom. So I often urinated into a bottle & then I emptied this bottle containing my fresh urine onto my private balcony attached to my bedroom. What do you think of that?

Contact your service provider and ask them to send an update to the phone.

They send you a specially formatted text message that automatically reconfigures the phone to work with "their" system.
They may also need to know that you have an iphone (with built-in voicemail) rather than a phone where you manually have to dial in to the voicemail system, to allow things to work properly together.