Coinbase hopelessly useless and unhelpful

After my recent experience, I think Coinbase is the most useless company in the universe. I've been trying to sell the little bitcoin and ethereum holding for a week without success. Their so-called support/help is non-existent - you just go round in circles chatting to the useless bot. Sending an email doesn't help - they refer you back to the hopelessly useless bot. In short, you go nowhere. When I get to the sell screen, it keeps asking me to add a payment method, which I've done a zillion times.