Samsung
Send a Group Text Message auf Samsung
Samsung Messages lets you message several people in two ways. You can tap in individual contacts one at a time, or you can pull in an entire saved group with a single tap. The second option only works if that group already exists in your Contacts app.
To use it, open a new conversation and choose the group option instead of adding people by hand. The full path is Tap on Messages ➔ Tap on Add conversation ➔ Tap on Add ➔ Tap on Groups ➔ Choose a Group ➔ Select the desired Contacts and tap Done ➔ Enter a Text message and tap on Send.
Once you confirm the recipients, everyone in that group is added to the message at once, and you type your text just like a normal SMS. If no group exists yet, you still need to add each contact manually, since Messages cannot create a group on the fly during this flow.
Whether replies land in one shared thread or come back as separate messages depends on your carrier and on whether group messaging (MMS) is enabled on the device. If you only need to reach the same people occasionally, adding them individually is fine. If it is a recurring group chat, saving them as a group in Contacts first saves time every time you message them.