iPhone: Cannot text alternate contact numbers separately

After 20 years of iphone use, I can no longer text alternate contact numbers!

--Apple 15, 1.5 years old

--IOS 26.5.2

--Everything else working fine

--I have rebooted several times, I have toggle every messaging switch possible, no go!

2 texting methods for alternate numbers, both fail:

1. texting from a specific contact:

it used to be that I could select any contact number with a text bubble next to it (I keep all alt numbers for contacts within 1 contact, I have a lot of people in couples (husband/wife), with home cells, business cells, etc) the text window would open and off I go.

2--texting from scratch from text icon in screen corner:

Hit text icon, select name from To: field, select any number in that contact by using little arrow to the right of the desired number... FAIL... I get sent to the text messages of the other number!!!!!

I used to be able to text distinctly to different numbers within a contact. I don't want the business texts all merged with the personal texts!!!!

I don't know when this happened, but it's extremely annoying.

There are couples whom I really only know one half of the couple, or who have grown up kids I don't know well, but if I need to reach the other half of the couple, or a kid, which I've always kept in the same contact, under different labels, I don't want to be in the same thread as the main contact number!!!

What the H, how can we fix this!!!

Am I going to have to take 500 contacts and split them so I only have one phone per contact %&? ... then what is the point of having various numbers per contact!!!!!!!!!!!

POST NOTE from this help process. I saved a screen shot to show this to you, but Apple for some reason DOES NOT accept iphone screenshots... I had to convert the iphone screenshot from an .heic to a .jpg ... ... ... sigh... why!

[Edited by Moderator]