Transaction mined but state variables aren't changing

I am able to get the transaction with a block number while calling method of a contract however the state variables don’t change unless I mention the “address” and “gas” parameters on web3^0.20.7

HelloWorld.sol

contract HelloWorld {
  string message;
  event evntGetMessage(string message);

  constructor(string mymessage) public {
    message =  mymessage;
  emit evntGetMessage(message);
  }

  function getMessage() external view returns(string) {
    return message;
  }

  function welcomeMssg(string name) external returns (string){
     message =  string(abi.encodePacked(message, " ", name));
     emit evntGetMessage(message);
     return string(abi.encodePacked(message, " ", name));
  } 
}

txn.js

//txn.js file to call the contract instance from web3. I have deployed the contract using web3 JS:

contractInstance.welcomeMssg('Hi',{gas: 500000,from:txnAccount1})   //returning me the expected results and appending the state variable - "message"

contractInstance.welcomeMssg('Hi')    //returning me transaction block number but not updating the "message" variable

Is it the expected behavior in [email protected]?

Thanks