If you feel this is unacceptable then you must confront them.
I'm sure they will be fine about it.
I had a customer this summer that I fitted an unvented cylinder for. His Vented cylinder wasn't that old. He asked me is it worth putting on eBay? I said yes give it a go. So I left it for him.
I had this customer years back that needed a plumber to get a restaurant completed in time for a certain date. I agreed to help him. As this was a very important job/customer
First day a Saturday , I ripped out the existing plumbing. Copper mainly.
He wasn't letting me have a sniff of it.
I never knew if he met his deadline.