I bought an item online. The sender gave me the wrong tracking number, so I thought the parcel is missing (ending up in some other address). She also checked, hence she sent me another package.
But it turns out that the parcel showed up. So that means I'm going to get two parcels for the price of one. What should I do? She wants me to return one of the parcels, but returning it would cost me a lot because I'll be returning it to the US, whereas I'm in Australia. Should I just keep it?
This sounds like the seller's mistake, so the seller should bear the responsibility for getting it returned. You could ask for her to arrange pre-paid shipping, or offer to get an estimate of the cost, making it clear that she would need to pay you that in advance.
If she chooses not to pay for this then it's up to her to tell you what to do with the second copy. You certainly shouldn't treat it as your own without her agreement, unless she doesn't make any arrangements for it in a reasonable time (several months).
The answer is probably much simpler than you think...
Refuse the second parcel. Contact the courier and tell them you do not want to receive the shipment.
They will automatically return the package to the seller as part of the courier service.
If they dropped off the package, take it to the courier and tell them to return to sender. Obviously do not open it. The return to sender option should be free for you.
Ask the seller. Offer to send it back to them if they pay the shipping. If you can use a second one of the item, you may offer to to buy it at half price or some similar deal.
Different countries will have different laws about this type of situation. I don't know what Australian law says about this.
For example, in the UK it is illegal for you to prevent the supplier from taking back an item that was sent incorrectly, but you don't have to send it back yourself, and you certainly don't have to spend your own money to send it back.
But while the package is "in your possession", you have a "duty of care " to keep it in good condition, and take reasonable precautions against someone stealing it, etc - i.e. you have to look after it as if it was your own property.
For example you can't just put it outside your house and leave it in the rain for a month, until the supplier sends a courier to collect it!
In the UK, you should contact the supplier and agree on a way for them to collect it at a time that is convenient for you as well as for them. Usually, they would get a parcel delivery company (like DHL or FedEx) to collect it from your house, at their expense. That way, the courier's paperwork (signed by you) shows that they actually did collect it, and if anything else goes wrong after that point in time, it's not your problem!
For a relatively cheap item, the cost to the company of collecting the item may be more than it is worth, so they might agree to let you keep it - but in the UK you don't have any legal right to demand that they do that.
Answers that suggest you should just send it back if the seller agrees to pay shipping ignore the cost in wasted time for you that shipping it back would incur. If it's something you normally do anyway, feel free to offer to do it to be nice. But if you don't have a printer at home to print the shipping label, or have to drive/travel a significant distance to a parcel shipping facility, or anything like this, it's unreasonable for the seller to expect you to do this for them for free.
For items under a certain minimum value (probably around $25) I would be inclined to just tell them they're out of luck unless they want to make shipping arrangements that don't inconvenience you at all. For valuable items where it's clear that you can't just keep it, they should compensate you for expenses incurred getting it back to them aside from just shipping cost (the "handling" part in "shipping and handling").
This is actually one of the main reasons I use a certain very large online retailer - when I occasionally do have to return small items due to a problem with the item (e.g. not matching description), they just refund it without requesting it be shipped back if it's under a certain value, saving a lot of time and headache that would otherwise make me just keep the item at a (monetary) loss to myself.
Ask seller if she will pay you for sending it back, if yes, then send. If she says you have to pay for shipping tell her that is because of her own mistake then why you should pay for that? If she still wants you to send by your own payment of shipping charges then just keep it with you and enjoy.
