iPhone calling other iPhone on it's own ?

My iPhone 7 has been calling my mom's iPhone X, but I'm not the one doing it? It's been doing this for a week, about once every other day, sometimes twice a day. I have absolutely no idea how this happens. The calls don't show up on my call history, but it does on hers. I don't know what happens when she answers it. My iPhone is about 2 years old, never been broken before. I've restarted it and it didn't help.