This is happening to us, too. I noticed we keep getting emails about past due invoices, but everytime we ship with UPS, we pay at the time of shipping so we should not have been getting any overcharges. I made a call with UPS, told them the acceptance scans are no where close to where we even ship out. They’re done in Stafford, TX, California, and other odd states. We’re in NY. The rep even gave me the names of the receivers, but of course theres only an address on the shippers.
I went through every invoice with the rep, and let her know not once single address was in our system and none were accepted anywhere near our shop, where we personally drop off. Its not a shopify problem at all, its UPS having such a terrible loophole for scammers to take advantage of people who utilize a UPS account.