Calling 23:31 at night, EVERY NIGHT

I am really annoyed and want feedback asap. I want to join Cartrack with a new vehicle purchased. Cartrack must still do the installation. I have set up an appointment for next week for fitment. They keep on calling me at 23:31 at night, when i answer, they simple laugh and drop the call. I want this number traced to get to the bottom of this. I am cancelling my membership due to this. Its harrassment and going to take this further. I WANT FEEDBACK ASAP.