They cannot fix their broken app & website

I cannot use my UBER business account, because the app & website gives me a promotion code error after NOT applying any promo code. I want to pay the full price, but cannot get past the error. Twitter helpline sends me the same pre empted response 6 times after sending them screenshots of the issue and proof that their "resolution" isn't working. Now they won't respond & am sorry they cannot assist me with useful advice? If the app is broken, log an IT ticket and get back to me? Surely this shouldn't be such an issue. Really frustrated.