Discovery Banking App not useable on my phone

My Discovery card, like others, has now been moved to Discovery Bank. I managed to get the new card relatively easily but have totally been stuck on not being able to use the Bank app. Because of the card, I have an account with Discovery Bank, however, when I try to go into my account on my phone, it tells me I don't have an account, I must register. So then I try to register and it tells me someone with that cell phone already has an account. There is no winning. I cannot tell you how many times we have spoken to Discovery about this and each time, they say they are going to change something on their side, to please give it a day or two. Now, weeks later, it remains the same and nothing has happened., I don't really see the point of phoning again.... maybe just change my credit card..??