Unanswered international calls and errors with discovery travel /banking

I needed to call discovery bank because the banking app says I should get 35% discount on an international flight, yet when I try book there is only 10% discount available. Anyway that is not resolved yet, they don't accept email queries but provide an international number, after 24 mins waiting to get an operator to pick up no one answers, simply pathetic and they actually don't want to help.