Using Contract to trade on mimo.exchange

MyTrade.sol

pragma solidity >=0.5.10;

import "./SafeMath.sol";
import "./IMimoExchange.sol";

contract MyTrade {
  using SafeMath for uint256;

  IMimoExchange public mimoExchange = IMimoExchange(0xb3972201f3Ae2b382665ca129Bd28d056758DBe2);
  address public vitatoken = 0xB8744aE4032Be5E5ef9FaB94ee9C3bf38D5D2AE0;

  constructor() public {}

  function buyvita() public payable {
    uint256 vitaBought = mimoExchange.iotxToTokenSwapInput.value(msg.value)(msg.value * 70, block.timestamp * 2);
    _safeErc20Transfer(msg.sender, vitaBought);
  }

  function _safeErc20Transfer(address _to, uint256 _amount) internal {
    (bool success, bytes memory data) = vitatoken.call(abi.encodeWithSelector(0xa9059cbb, _to, _amount));
    require(success, "not enough tokens");
  }
}