Creating a token swap - but unable to swap native tokens

Hi All,

I have created a swap contract that can swap tokens for tokens, but im unable to work out how to swap native tokens.

I can swap WBNB, but not BNB to other tokens ?
Not entirely sure what I am missing.

The code takes the contract address for the tokens and then does a "swapExactTokensForTokensSupportingFeeOnTransferTokens" call to swap token-token.

How could i change the below code to accept BNB tokens?

function SwapTokensForTokens(address _tokenIn, uint amountIn, uint256 _amountOutMin) external {
        IERC20(_tokenIn).transferFrom(msg.sender, address(this), amountIn);
        IERC20(_tokenIn).approve(address(uniswap), amountIn);

        address[] memory path;
        if (_tokenIn == uniswap.WETH()) {
            path = new address[](2);
            path[0] = _tokenIn;
            path[1] = tokenToSwap;
        } else {
            path = new address[](3);
            path[0] = _tokenIn;
            path[1] = uniswap.WETH();
            path[2] = tokenToSwap;