I've had something like this happen twice. The first time a company shipped me something I ordered, and then a few days later something I didn't. I let them know, and they sent me a prepaid return sticker, and scheduled for UPS to come pick it up, they told me to just leave it on my porch.
No problem there, I was happy to get them their stuff back because it wasn't any issue for me. I didn't have to expend any real time and effort fixing their mistake. A quick e-mail to them, and then slap a label on it (they actually mailed me one) and drop the box on my porch.
Another time an eBay seller fucked up an order bad. They shipped some fairly cheap headphones I had purchased to a guy, and instead shipped me two McIntosh monoblock tube amplifiers worth about $10,000 each that he had purchased. I was a little perplexed by these massive 100 pound each boxes when I expected headphones
Well they were annoyed at me that I didn't refuse the delivery "like I should have" (I wasn't there, the apartment manager accepted packages for us) and wanted me to take them to UPS and ship them to the other buyer. They said they'd refund the shipping charge when he got the amps. I told them to fuck off, they could send me shipping labels and have them picked up, or go away. The were butthurt about that, but finally agreed.
So depends on how the company has acted. If they truly are making it no hassle on the part of the customer: As in willing to send them a shipping label (and if necessary a box) and schedule a pickup, then ok. However if they expect the customer to go out of their way to fix the fuckup, then no. Sometimes what they mean by "no inconvenience" is really "We want you to deal with the hassle of a return, then we'll refund you the money for shipping later, maybe."
When they are the ones that fuck up, it is their duty to make it right, with as little impact on you as possible.