False advertising MONEY ****

My mother made a booking at the Southern Sun hotel at OR Tambo for the 30th of September but then later on the day called the hotel letting them know she will not be checking in/cancelling her reservation which on the app she used to book had said there's free cancellation and only pay when she gets to the property however they then charged her card for the full fair the following day on the 1st of October. She immediately called the hotel which told her to get back to the app she used to book and when she did that the app helped as far as they could even showing proof that the issue is now on the of the hotel, she was then contacted by the hotel personal asking for her to reiterate the story which she did via email and then then responsed saying she will only get half her booking fee back which is not fair as the advertising on the app said no prepayment and free cancellation which my mother followed to the tee on both the booking.com app and which the Sun international hotel so how is she then told that only half pf her money is coming back after it was taken *******ly at the in the first place make it make sense how she is made to pay for a booking she never used and canceled prior to check in times and within the apps free cancellation time frame