OK I once bought some stuff online, and $250 of extra stuff showed up in the box that wasn't on the invoice, I didn't order, or pay for it.
It was not something I needed, or would buy, but could use....'at the right price'.
I contacted the shipper, a big online retailer of aquarium supplies, and they were happy to sell the stuff to me at 50% off the discounted catalog price.
It was also something that was not tiny, and the shipping back to them wouldn't be real cheap.
This worked out because it was something I could use. The batteries? Wouldn't make too much of an effort, unless they sent a prepaid return box or something.
Not sure how many cells those are, or the 'C' rating, but the price could range from $10 up, each, and how useful they are to somebody local to you who does RC stuff depends on the power connector, which vary quite a bit. (But can be changed if you can solder a little)