Cast to work on a film at the end of April, credit keeps getting declined even after offering proof of role and employment

I've been cast to work on a film at the end of April, a good character role, and have submitted the credit now 5 times and had it declined because it "cannot be verified." First I posted an email from my agent I had been cast, then sent them a copy of my paperwork for the show, then gave them the phone number and email of the payroll department contact, then gave them the phone number of one of the AD's on the show who just set up my wardrobe fitting for me. What do they want me to provide as proof of this employment and credit? I'm sure one of the producers would verify this role and credit, but I don't like to bug these people with something so mundane and simple as this, it should be easy and a no brainer.