If there truly not choice (express= signature and cust chose express) then maybe amazon will remove the complaint since its not an option. Worth a shot. And yes its inconvenient but it protects everyone. I state in my ebay listings its required,(for items of high value) if you dont like it, dont buy it.

Customer is annoying. They probably scam people if they are unhappy to sign. In most cases signature is proof of delivery and buyers can’t fight that. If no signature, buyers can claim non receipt and win. Happens all the time. People know the system and abuse it to their advantage.