while($csClientes = mysqli_fetch_object($sqlClientes)){
            $visualizar .= "<tr>";
            $visualizar .= "<td style='font-weight: bold'><i class="fas fa-caret-right"></i> ".$csClientes->NomeCompleto."</td>";
            $visualizar .= "<td style='text-align: center;'>R$ ".number_format($csClientes->ValorTotal,2,',','.')."</td>";
            $visualizar .= "<td style='text-align: center'><span class='status'><a href='#!' id='btnAlterar' data-id='".$csClientes->IdFinanceiro."' class='btn btn-danger btn-xs'>Pendente</a></span></td>";
            $visualizar .= "</tr>";
    }

<script>
$(document).on('click',"#btnAlterar", function(){
  var IdFinanceiro = $(this).attr('data-id');
    $.post('sistema/alterar-status.php', {key: IdFinanceiro}, function(retorno){
    if(retorno == 1){
      $(".status").html("<a href='#!' id='btnAlterar' data-id='<?php echo $csClientes->IdFinanceiro; ?>' class='btn btn-success btn-xs'>Pago</a>");
    }else{
      $(".status").html("<a href='#!' id='btnAlterar' data-id='<?php echo $csClientes->IdFinanceiro; ?>' class='btn btn-danger btn-xs'>Pendente</a>");
    }
    });
});
</script>

<script>
    $(document).on('click',"#btnAlterar", function(){
      var IdFinanceiro = $(this).attr('data-id');
        $.post('sistema/alterar-status.php', {key: IdFinanceiro}, function(retorno){
        if(retorno == 1){
           $("#statusPago").css('display','block')");
           $("#statusAberto").css('display','none')");
        }else{
           $("#statusAberto").css('display','block')");
           $("#statusPago").css('display','none')");
        }
        });
    });
    </script>

<td style='text-align: center'>
                           <span id='statusAberto' style='display: block'><a href='#!' id='btnAlterar' data-id="<?php echo $csClientes->IdFinanceiro; ?>" class='btn btn-danger btn-xs'>Pendente</a></span>
                           <span id='statusPago' style='display: none'><a href='#!' id='btnAlterar' data-id="<?php echo $csClientes->IdFinanceiro; ?>" class='btn btn-success btn-xs'>Pago</a></span>
    </td>

$sql = mysqli_query($this->conexao,"UPDATE pagamentos SET StatusPagamento = 'P' WHERE IdPagamento = '".$_POST["key"]."';");
if(mysqli_affected_rows($this->conexao) > 0){
  echo '1';
}else{
  echo '0';
}