Can I swap my USDT (erc20) to ethereum with eth charges?
You can easily swap your USDT tokens to ETH in uniswap but for this your wallet need to have enough ETH to cover gas fee. If you want to swap USDT to ETH without having gas fee covered you can use 1inch (app.1inch.io) to swap USDT to ETH using fusion swap router. 1inch has fusion swap which takes no fee to sell your ERC20 token to ETH and ETH to other assets. But in that case too you have to approve USDT spend to 1inch router. So, even in 1inch you need to have enough ETH in your wallet to cover gas fee first time which is required to approve the token.