Some bottles are refill only, some bottles are exchange only and some bottles swing both ways 🤨.
The beauty of exchange bottles is you hand the old one in and you get a full one back. The beauty of a refill bottles is you get to stand in a queue and wait for the refill elf to fill the bottle up. As a bonus you also get your original bottle back and most importantly you only pay for what actually went into the bottle.
We weigh every bottle before we top-up and you only pay for the difference.
A serious nuisance with the refill bottles is that you have to be there in person, kinda like home affairs and ID books but without the profound inefficiency and bureaucracy. Also our system isn't always down.
One of our values is to "break china for the client" which means bending over backwards to solve nuisances where we can - scratching your itches if you will. So we now run a collect and refill and return service. It's clunky and it's never gonna make us rich, but it does make your life a little easier if getting you bottle refilled is problematic for you.