Technology not so helpful anymore

Relly ABSA. I don't thin **** this nonsense anymore. Phone and you get a bod to talk to. Go on the internet and chat with a bod. I need somebody with brains to guide met throught my problem. I am trying to make a payment to a new customert and ABSA says I must use the listed customers at ABSA. I then go to the listed customer and ABSA adds all the info but at the end it gives me an error message. 013 - Enter a valid beneficiary account number. This has been the number on the list. So why won't it take that number.