Belle Clay Co
I was excited when I first got this app and their customer service is great but the app has limitations and was not tested properly. I had a lot of customers with multiple orders in a day and the merge was all over the place. I had to manually review all of my orders and manually merged them. The shipping refund did not work correctly if you have more than 2 orders merged.
Update: we've made some major updates to the app, any chance you'd test it again and let us know if you find any issues again? We also now have 2 full-time developers so any bugs/new features you'll need will come out much faster now.
I apologize for the bad experience you've had so far and I wish you'd give us another chance.