Unfortunately the problem is that you're dealing with a retailer that sells many items other than just steelbooks.
Same with Amazon, Best Buy, HMV and others like them.
When you complain to a customer service department it's not like the person taking the complaint is where the warehouse is.
They can't walk down to the warehouse, pick out your replacement copy and make sure they put it in the white cardboard box that you want.
They probably log your complaint into the computer system indicating that you need a replacement with no mention about a proper steelbook package because they probably don't even know what the steelbook white box is.
So I doubt a manager or supervisor sees that the problem is that it wasn't shipped in a white box.
The replacement request goes to the warehouse and the order is filled and packed in whatever packaging the picker that was hired 10 minutes before has been shown to use or has available by the guy who trained him (who was probably hired the day before.) They probably fill orders for amarays, funkos, monopoly games and every other item Zavvi sells.
Like I said, it's the same as Amazon {millions of items), Best Buy (appliances, computers, cell phones, furniture) HMV (CD's, movies, t-shirts and so on).
Steelbooks are not a priority to any of these companies. Just another product they sell.
If any of these companies stopped selling steelbooks, they would never notice it when it comes to the bottom line.
Therefore it will never, ever, get better. Nothing you can do to ever make them change the way they do things.
Different story with premium steelbook retailers. And yet they still ship items with quality control problems at times.
But at least their shipping packaging is good!