app for easily grouping contacts on iphone

Hi all, I have a group of support workers I message. From time to time, some support workers are no longer working, or I find new ones I need to add to the group. As a result, I need to compose a new message and add everyone from scratch again, because, once created I do not appear to add new contacts to an existing group in the messages app and I am unable to create a group to text from the phone contacts app. As you can imagine, this is very time consuming and annoying having to compose a new message and make sure I've added all my current support workers still working and add the new ones and make sure not to add those who are no longer support workers. After doing some research, I found an app called groups, but this app is not very accessible. If anyone knows of an accessible app that allows me to create a group and easily add or remove contacts before sending a text via the native messages app, that would be greatly appreciated. Thanks heaps in advance. Looking forward to hearing from you. :)