It's good to know what to do about receipts, online invoices troubleshooting when things go wrong. Even though we all hope it never happens, errors do happen, and having a troubleshooting plan in mind can make a world of a difference.
Prevention first. If at all possible, PRINT out your online invoices, or receipts (as some of us more mature people used to call them).
Some say it is safe to store invoices from online purchases on your computer as a file, or at some online 'cloud' (storage site), however, if you really want to be safe, print out the online invoice. If you have no access to a working printer, I can empathize. But then I would still save the receipts in a folder with definite plans to get the online invoices printed out as soon as possible. Maybe from a friend's computer and printer.
If anything should go wrong with your purchase order or delivery, you can go back to that store's site and find their phone number and phone them to work through the problem and troubleshoot the issue. But they will ask for information that you can only find on the online invoice, such as your order number.
If they ask you to send them the invoice, make sure to first scan/photocopy it, or print out another copy, so that you will still have a copy of your online invoice in your own possession.
Check the online store's Terms of Service ahead of time before deciding to buy. If you have any problems go look for that document again on their site, and check to see if it has changed. You need to know what they are willing to do, and in what instances you are on your own.
Don't accuse and jump to conclusions too fast, writing the shop off as evil. Contact the store's manager or owner, explain politely the situation as far as you understand it, and ask them to look into it. There's no need to feel either timid or irrate. Just be polite and firm about asking for and expecting their help to resolve the matter of your invoice, or shipping, or delivery of your purchase. If they should become irrate or angry, just say quietly but firmly, "I'll be asking other authorities to check into this for me." Then hang up.
If a problem appears before you get delivery, or immediately after the purchase, you can stop the payment by notifying your credit card company, and asking them NOT to pay out that online invoice.
If you used a debit card; it is treated like cash, so you are not so likely to be able to cancel payment. You may have to settle for a gift card from the store if they cannot help you resolve your problem. Or, you may have to purchase something else for that amount.
If you are ultimately ripped off by a certain online store, you should report them in several places;
your own local police (they may have information on previous fraud by this merchant and may need your evidence).
The store site in question, or its parent company, may have a link called something like "Report Abuse here" - contact whomever you can there to report your problem. They have a right to know first about their poor customer support - not from the media or a third party. Write to the Chief Executive Officer (CEO) to explain what happened, and what you have done to resolve it so far. If you want a refund, ask for it.
(Do try to work it out with the regular employees first. Innocent glitches can happen, and you would want someone else to give you that opportunity to correct it if you were in their shoes, or had an online store).
If no one listens to you, or deals with the matter, please report that store to the right authorities. The Better Business Bureau might be one. You could also lodge some reports online such the the Shopper Grade, and ResellerRatings.com, and other scam forums. This will alert others to be careful enough to research a shop before they buy there.
If the situation calls for extreme measures to warn others, you might consider writing up a press release or telling a reporter your story. Be careful though for bad publicity has killed some businesses.