Poor App performance.

I trying to make a purchase online on the Woolworths app but the App doesn't give me the option to make payment. I have called their online number for assistance, they said I must delete the App and install it again, nothing. They said I must refresh the App and confirm the delivery address but still nothing. I am so frustrated now because they are not providing me with the assistance I need. What is the purpose of a mobile shopping App if it won't provide the convenience it promises?