Then suck their teeth and say it won't fit in their trolley!
Or, you leave it in a named location for them if you're not in and they claim it wasn't there.
When they turn up the next day and are grilled in full Glaswegian mode by the wife they then admit they left it as they couldn't fit it in their trolley. Try to do a runner until wifey pens them in and insists they call their supervisor!
FFS, the ones round here are lazy f*ckwits who look for any excuse not to do their job.
The next day I left a message on the post box............... "Dear Postie, no awfully complicated collections for you today as Evri have it all sorted at half the price. Hope you haven't strained anything reading this note."