I think they simply wanted to check if you're one of those people who send out tens (or even hundreds) of resumes and then wait if somebody responds, or if you did some research and you're really interested to work for this specific company.
By trying to reschedule the call for no obvious reason, it most likely seemed to them like you belong on into the former group and they obviously aren't interested in you anymore.
As for actual advice, you should learn from this experience, there's nothing better you can do.