Bolt South Africa

I used Bolt for the first time yesterday and paid the fee quoted but when I was dropped off the fee was more than double that I was quoted ther was even a waiting fee included although I never moved from the spot when the ride was confirmed, I eventually received a note to say I received a 50% discount but the fee was still more than what I was quoted, the scary thing is that they have direct access to your account and before you know it your account was already billed with the additional amount. The question is how can you trust them??????????