Have you tried my suggestion if you still have some balance on other addresses in your copay extracting private keys from your backup seed or wallet.json.aes is I think the best solution to take control of the address that still has funds and transfer it right away to another wallet like Electrum.
Never had any experience using copay but since they have backup seed or file there is still a chance that you can get the remaining funds in your wallet without contacting copay since they said they don't have control of your wallet.
So if I were you start extracting private keys from the seed or backup file before it transfers again to an unknown address.