I compiled smart contract in solidity on remix.ethereum.org. I made account via MetaMask and want to let other addresses send tokens to themselves using ropsten network. I mean - I am contract owner = A, transfer some tokens to B and let him transfer/withdraw his tokens to address C. There are two transfer functions:

• transfer, send tokens from contract owner to receiver address and it's working properly
• transferFrom, is causing problems, send tokens from B to C. I tried to use it via remix, write contract on etherscan and with web3.py but all of them return error.

Firstly I deployed contract with 1000000 tokens (1000.000 with 3 decimals) and sent 1000 (1.000) tokens to B (balanceOf(B) returned 1000), then called approve function with 1000 tokens for B address (allowance returned true), and called transferFrom, which threw errors:

• remix: "Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending? gas required exceeds allowance (8000029) or always failing transaction"
• MetaMask on etherscan: "ALERT: Transaction Error. Exception thrown in contract code."

Another weird thing is sending tokens via transferFrom function from contract owner's address works properly like normal transfer. Also transfer exaclty 0 tokens from B to C works normally. I can not figure out what is wrong, below is contract code:

pragma solidity >=0.4.22 <0.7.0;

contract AnotherCoin {

    string public constant name = "AnotherCoin";
    string public constant symbol = "ATC";
    uint8 public constant decimals = 3;  


    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
    event Transfer(address indexed from, address indexed to, uint tokens);


    mapping(address => uint256) balances;

    mapping(address => mapping (address => uint256)) allowed;
    
    uint256 totalSupply_;

    using SafeMath for uint256;


    constructor(uint256 total) public {  
        totalSupply_ = total;
        balances[msg.sender] = totalSupply_;
    }  

    function totalSupply() public view returns (uint256) {
        return totalSupply_;
    }
    
    function balanceOf(address tokenOwner) public view returns (uint) {
        return balances[tokenOwner];
    }

    function transfer(address receiver, uint numTokens) public returns (bool) {
        require(numTokens <= balances[msg.sender]);
        balances[msg.sender] = balances[msg.sender].sub(numTokens);
        balances[receiver] = balances[receiver].add(numTokens);
        emit Transfer(msg.sender, receiver, numTokens);
        return true;
    }

    function approve(address delegate, uint numTokens) public returns (bool) {
        allowed[msg.sender][delegate] = numTokens;
        emit Approval(msg.sender, delegate, numTokens);
        return true;
    }

    function allowance(address owner, address delegate) public view returns (uint) {
        return allowed[owner][delegate];
    }

    function transferFrom(address owner, address buyer, uint numTokens) public payable returns (bool) {
        require(numTokens <= balances[owner]);    
        require(numTokens <= allowed[owner][msg.sender]);
    
        balances[owner] = balances[owner].sub(numTokens);
        allowed[owner][msg.sender] = allowed[owner][msg.sender].sub(numTokens);
        balances[buyer] = balances[buyer].add(numTokens);
        emit Transfer(owner, buyer, numTokens);
        return true;
    }
}

library SafeMath { 
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
      assert(b <= a);
      return a - b;
    }
    
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
      uint256 c = a + b;
      assert(c >= a);
      return c;
    }
}

I tried compile it on different compiler versions (4.x, 5.x, 6.x) and compilation was succesfull but this single function throw errors. Similiar topics on stack didn't bring the solution.