I buy things online a lot. Almost always from Amazon, and let me tell you that they are good. I have always gotten quick responses and and great results. Example: I tried to buy some music using promo codes and while the codes seemed responsive they charged my credit card. The let me know that the codes where inactive when I asked and they refunded my card and gave me 5$ free for using on their mp3 platform. More companies need to learn that even after someone buys your product that you do your damnedest to make them want to keep using your services.
Another example would be the company Anker. They reply within 24 hours, they are willing to help, and they are nice. They know that if you are having issues that it is their job to help you out. I recently had an issue with one of the mice I bought from them and they where willing to refund and pay for the shipping.
These companies are to be trusted and have proved it time and time again.