Uber Eats

I am in the possession of a Uber EAts Promotional Code. I have app**** the voucher and it shows credits, but the app does not refresh my credit hence asking me to pay the full value of the meal, which should have been taken off the credit, since my order is less than my available credits. I have been embarrassed when I went to pick up my order at the store only for them to turn me away saying that I need to pay. I dont understand why there is no contact numbers for this Uber EATS, only stupid FAQ which does not help. I only received a irrelevant response to my query later today which still has'nt been sorted. Why have an app when it does not allow you to even query things in real time.. so pointless!!!! I am regrettably unhappy with Uber EAts and their feedback.