After endless contact still no refund

I rented a car at the airport from the 3rd to the 15th of January, Rental agreement number: ********** . Upon collecting the vehicle I was informed that the additional driver was supposed to sign as well. She was not present and I therefore requested to cancel the add on to my agreement. The staff member whose badge stated "Trainee" advised that she would make a note on my agreement. Upon delivery of the car I advised the collection manager of the same who said she would make a note as well. On the 18th and 30th of January I sent emails to ********** and ********** regarding this with no feedback. I also spoke to Samantha on 30th but the line was bad so the call ended. I am currently in South Korea and therefore only have online recourse since the telephonic option failed. A month later and I have yet to receive feedback. Please action this as soon as possible or I will be forced to take further action.