Avantree

They don't provide technical support unless you can provide an Amazon order number. Bit difficult if you're not the person who ordered it and cannot contact the person who did. Not sure why they need and order number at all in order to try to help fix an issue with their product: plenty of companies will help over Twitter etc. without you having to prove you bought the product form Amazon.

Excellent customer service. I received a Bluetooth speaker for the car for Christmas but it wouldn't charge so they sent me a new one free without any hassle. They also sent me a return label for the broken one. They were very prompt replying to my emails and were courteous. Can't fault them.