No group message option in iMessage option in settings

The Group Message option is not an iMessage option, it is an MMS message option. It will disappear if you have MMS Messaging turned off. It is also possible that it could be related to your cellular carrier/plan. The following quotation is from http://support.apple.com/kb/HT5760

The Group Messaging setting applies only to MMS messages.

• Your wireless carrier may restrict the maximum number of recipients allowed in a group message with MMS.
• Disabling Group Messaging has no effect on iMessage behavior. Responses to group iMessages are always sent to all recipients.
• Group messaging with MMS requires an appropriate plan from your carrier for use on iPhone.
• Carrier messaging rates may apply when using group messaging with MMS.

I've had success making a group chat with two android phones. But I have the "group messaging" setting turned on. However, I have noticed that some iPhones do not have this setting (at all) on their phone (some of which are the same model phone and on the same carrier). Another interesting fact (as MJsenior pointed out) the iPhones that don't have the "group messaging" setting shown, the plan or carrier "does not support group messaging." While an Android phone on the carrier and same plan can group message just fine. So much for "iPhones, they just work."

Bell Canada does not support it while telus and rogers do, not sure which US carriers do. Just in case anyone else is searching for an answer like I was. Put in a different carrier sim and the option works fine.

When I asked bell corporate service they just say they do not support it... Which seems pretty sloppy in this day and age.

im having the same issue. any solutions?? iphone 6s