Who's calling Again?

As I took my lunch time at around 2:00 pm, our phone rang. I immediately picked it up and answered it. Nobody was answering back. All I hear are beeps. This time there is a phone number that was registered on our phone. In contrary to what is always happening wherein we always have anonymous callers, this time there is a number being registered. The phone rang again the second time. It was the same number. Again when I answer, all I hear are only beeps. I just waited till I finished my lunch before it gets cold. After eating my food, I dialled the number that was registered on the phone. A lady answered back. I asked her if she called to our number but she said no. what's happening now? who's calling anyway? that's the answer I can't give you.