I filed a A-Z claim through amazon for a defective bicycle that I purchased and amazon approved the claim and updated my order to "seller approved your refund". The item was returned to the seller with a tracking number but I never received the promised refund from either amazon or the seller. I contacted amazon through their online chat and also on the phone on many (10+) occasions but have not been able to get anywhere. The most recent information they told me is that my claim was "denied" after it had been originally approved! I don't know what to do next. Should I write a letter? If so, to whom should I address the letter?