Have a heart - perhaps they are working? from home & can't be arsed when they see who is calling.
Seriously, it's a common problem - limited oversight of productivity & no one seems to bother to tie the loose ends; checking/validation gets left to the client. Some say getting difficult with say the new business manager is often the answer, as they tend to be more proactive.
I'm having issues with a local healthcare provider, who I found had been double invoicing (me & BUPA) for the same tests. When I eventually chase someone down, the call gets interrupted by dogs barking, TV noise, kids screaming - hardly professional &, you guessed, once I put the phone down it's job done - none of the messy loose ends ever seem to get sorted out, so 14 days later I'm back to square one.