in product.tpl – customizable product

i’d like to change cols in order to make the textarea larger:

<textarea name=”textField{$field.id_customization_field}” class=”form-control customization_block_input” id=”textField{$customizationField}” rows=”3″ cols=”20″>

i try to put cols=”40″ but nothing change
when i put rows=”6″ it’s ok

what do i need to do to change number of cols of textarea???
thanks