pulling a fast one
You can't get mad at a brand for playing dirty when it's done in the most clever way possible.
DHL pulled a "fast" one their competition by sending out special packages via competitor services (e.g. UPS, FedEx, USPS, etc.) that when picked up, appeared to be plain black boxes, but changed to reveal a special message when carried around outside for delivery.
That special message their competitors had to walk around with? DHL is faster. Brilliant!