When you make a withdrawal of Polkadot from an exchange, be sure to select the official DOT token, as indicated in the example image below. 

The official DOT token lives on the Polkadot network and all DOT addresses start with 1. 

If you select any other option here, you choose a wrapped DOT version of the token, which lives on a different network such as Ethereum, Binance Smart Chain, Polygon, etc. Please be aware that these tokens cannot be sent to DOT addresses or transacted on the Polkadot network, as they are not compatible.

If you made a mistake here, please contact the exchange directly for assistance. In theory, you should be able to simply send the tokens back to your exchange account and then withdraw the correct token instead. Your individual exchange Support Team should have more details on that. 

Since these transactions do not take place on the Polkadot network, we are unable to help in this case.