Promo code promise not kept

I shared my promo code with some of my friends and then taxify decides to withhold the free rides due to me. I then contacted taxify and spoke to Cameron who told me to send in some documents so that they may unblock my account. When I sent the documents, he then responded that I may now only make cash payments. On the "free rides" page of the taxify app it states, and I quote "Share your promo code with friends and their first ride is free (up to R150). Once they've tried taxify, you'll get a free ride code via email." Taxify should be held liable to keep their promises!