Taxify ripping me off with overcharging my account mismatching what was shown on their app

For the past two days Taxify has charged me beyond the amount shown on their app as the driver ends the trip. On my statement it comes as overcharged. I requested Taxify on Wednesday 28/11/2018 from JHB CBD to Ridgeway nearby Shoprite and the app showed my +-R54 since I have a promo available on my account. The driver arrived on time by the destination and ended the trip but I received a msg from my bank with a receipt of R90 from that Taxify trip. Thursday 29/11/2018 I again requested Taxify for the same addresses and the app showed me +-R77 and the driver delayed the ending of the trip for like a minute and it was running on a promo also on my account. When I get a receipt from my bank I got R194 charged on my account by Taxify. Since I sent emails from their customer service not even an acknowledgement email response has been sent to me regarding my refund request. I called the driver and he said it’s their offices that deals with charging accounts.