If you'd like to send an SMS message to recipients in bulk, your mobile device settings may be configured to show each individual's phone number to all recipients of the message.  

For privacy and security reasons, you'll likely want to disable group messaging before sending bulk SMS messages. 

Here's how:

  1. Go to the "Settings" app on your Apple device
  2. Select "Messages". 
  3. Scroll to the "SMS/MMS" section and disable "Group Messaging". 

Once complete, your recipients won't be able to see each others phone numbers from a bulk SMS message. 

Note: If you're unable to locate "Group Messaging" on your settings, this likely means your carrier doesn't offer this service. This would be disabled by default.