I'm having an issue with a wedding. The groom and bride change the wedding date every two weeks. We weren't able to do our engagement shoot because they kept canceling. Wedding date was scheduled to December 2016, changed for February 2017, March 2017, now it's April 2017. At this point, I want to cancel and bill them for the work I've already done for them as per contract. Any advice regarding this would be much appreciated.