I have the following lines
$objPHPExcel->getActiveSheet(0)->freezePaneByColumnAndRow(0,4);
$objPHPExcel->getActiveSheet(0)->freezePane('A');
which gives me the following result: I intend to fix column A but I think that the line above does not allow me to do so
The method you are using is incorrect, you just have to put the following line.
$objPHPExcel->getActiveSheet(0)->freezePaneByColumnAndRow(0,4); // donde 0 es la columna desde donde se congela y 4 es la fila hasta donde se congela.
I leave this guide if you do not understand the difference between column and row: Columns and ranks