I recently purchased a 20,000mAh power bank from Cygnett. I had some issues with it and initially had trouble getting in contact with them however they responded after some time and explained that their customer support manager had left and that they were behind on some of their support tickets. They were very apologetic, sent me a new unit very promptly and were extremely helpful in resolving the issue. They'd even upgraded the replacement unit to a higher model and I didn't have to send the faulty one back. Fantastic service and will buy again! Thanks guys!