I hope I haven't asked this before. I recently tried to text someone using Messages on my mac. I have one person I know with a certain name but she is not in my contacts either on my Mac or my iPhone. Still the autofill works to make it possible to contact her. I got her number wrong by one number in the past and it went to a stranger. Now that number keeps popping up (with my friend's name). I forgot I had the wrong number AND the correct number showing up in my autofill, and I texted the wrong person again. Thankfully, they let me know (again). I cannot find a way to stop the autofill from using in both numbers. I always have to be careful not to use the wrong one.

I found this online, but it doesn't work for me since my friend is not technically in my contacts: In the Safari app on your Mac, choose Safari > Preferences.
Click AutoFill. To turn AutoFill off or on, select the information you want to include in AutoFill; deselect the rest. To change or delete AutoFill information, click Edit next to the information you want to change or delete.

Any help would be appreciated.

I am not sure where Messages is getting its list from, other than Contacts, but there is another contacts list in Mail > Window > Previous Contacts. You might look to see if the alternate number is there, and if it is delete it.

Hi: Thanks, JoeMike. I checked, but it only shows emails, no numbers.

You know, I think it works like the autofill works in Safari just remembering urls. They aren't stored anywhere obvious, but Safari remembers them. It's a mystery and very annoying. I couldn't find anyone on the internet who had the true answer. I was told there could be a link between my iPhone and my Mac with the numbers, but I was able to successfully remove the number from my iPhone but I still have the problem on Mac Messges. Oh well. I wonder if there is somewhere in the library that keeps that info. I used EasyFind but ony found a couple of deleted texts I had to the correct person.