Random Person Speaking Spanish On My Cell phone?

So I was having a conversation on the phone with my Dad when all the sudden I hear someone talking in Spanish,I don't know if they could hear me or not but I was like um Hello???? And I don't know if they were responding to me since I don't speak Spanish.It was apparent my Father wasn't on the call anymore so I preceded to hang up and call him back when I called him back he told me the call ended.But this is the second time I've heard a Spanish person talking both times when I talked to my father on his cell phone.