Hello Findkendwa,
Firstly, as I mentioned in this other thread here, there is no guarantee a device won't use other services when receiving SMS messages. If your device does use other services when it connects to the cellular networks, it will likely be considered roaming usage.
In simpliest terms, short messaging service (SMS) is strictly text or characters while multimedia messaging service (MMS) contains data.
@findkendwa wrote:
.. - Does this mean that if someone attaches a photo or video to you in a text it is automatically becomes an MMS?
Yes, any text message containing a photo or video is automatically converted to MMS.
@findkendwa wrote:
..Is iMessage an MMS?...
No, iMessage is neither SMS nor MMS. It is Apple's proprietary messaging service. It transmits as data and not as text messages. If transmitted over the cellular networks while abroad, it would be considered roaming data.
@findkendwa wrote:
... What does a "subject header" mean in a text?...
Essentially, a subject header (fields) in a text would be similar to that in an email. You can view more information regarding them here. If someone sent a message with a blank subject, it would still be considered a MMS.
@findkendwa wrote:
... Is a "group message" when a text is sent to two or more recipients? ...
It depends on the phone... I explained the SMS protocol previously here. In that post, I explained how old devices would send parts of a long message as separate SMS. Similarly, older devices would send group messages as individual SMS messages to each recipient. However, newer devices are able to use chat functions to keep those messages in a group. In doing so, those would be considered MMS.
@findkendwa wrote:
... also read somewhere that even a text that has an EMOJI in it is also an MMS. Is this true?
Not necessarily. As also explained in that post provided above, the use of emojis would limit the number of characters available in the text message. As shown here, an emoji does not necessarily convert SMS to MMS. However, what I did not show in that post was that if I continued to add more and more characters to exceed my device's SMS limit, it would automatically convert to MMS. It would have been shown as the remaining charaters/number of SMS switching to amount of data in kbs.
Unfortunately with iPhones, I am not aware of any 100% guaranteed method of ensuring the device does not use other services when connected to foreign networks. Another setting to consider disabling, though, would be text read or delivered receipts. When your device first connects to the foreign networks, it will receive the Welcome abroad text message. If your device provides the delivered or read receipts, those would be considered sent messages as well.
Hope this helps and doesn't add to your confusion 😀
Cheers
