Group messages sending as a multimedia message

[Anonymous]

There seems to be a few similar issues but none quite the same as mine;

About a month back I recieved a message from a friend saying O2 had sent her an email saying that I had sent her a photo. I thought this was rather strange but forgot about it, since then she has had 2 more of these messages. Again I just left it.

Now I have recieved my bill this month and I have been charged for 8 multimedia messages. Looking at the telephone numbers that these have been sent to, it is all the group texts that I have sent which involve the person above.

I have sent other group texts (and not been charged) but the ones that involve this girl have been.
Any idea why?

[MI5]

As I said above, Sony do not include this option, unfortunately 😞