Facetime Hacked?

My boyfriend and I were on FaceTime last night and we fell asleep with it still on. I woke up in the middle of the night and I saw that the FaceTime call was still on but was a GROUP FaceTime call with a random number that we didn't know. I hung up the call immediately and started doing research. I haven't found an answer. This hasn't happened before but I have gotten calls from random groups with like 20 people that I don't know along with text messages. What should I do? I was thinking about changing my number but I'm not sure.