it receives calls from my sister it just wont receive the texts she sends me, she has an iPhone, on her phone it says its sent to me but i don't get them, her messages send perfectly fine to everyone else but me and my phone receives everyone else messages just not hers, i can receive calls from her its just the texts, what is going on? how do i fix it?

by the way iv already tried turing it on and off again and getting a new sim card and she has already tried getting a new sim card to, is it something to do with the settings? please help!!!!