my mother tried to block me from sending media to people all together and she only succeeded in making it so I couldn't send media to anyone without an apple product. It's been a year and she and I both have no idea how to fix it. Every time I try to send some sort of media, that little red exclamation point comes up. We don't know how to fix it
Let's back up. Did you get a net SIM card when you got the iPhone?
did your mom set restrictions on the iPhone? ( settings, general, restrictions. She has to remember the PIN code she entered)