Discovery bank, does not honor its promise

I visited a discovery bank branch in menlyn on the 10th. I went there as I had a form that they needed to stamp and confirm that I do not have an account with them. The guy that was assisting me told me to send an email and they will send me the confirmation letter. He indicated that the SlA is 24 to 72 hours. I waited until I got tired. I called the customer line and they informed that actually I was supposed to attach the form and thereafter give them a call. That was not explained to me at the branch and mind you I am about to miss my deadline. I was given a case number to resend the email and attach the form and they will prioritize me. I spoke to a banker Hopolang. After 48 hours I called again and they said they have sent the letter. I am confirming that I did not receive anything. Should I miss my deadline due to poor service, training and efficiency will discovery bank be liable. I don't have a account with them. I do not understand why are they making me suffer like this.