Quote accepted and then changed

I received an sms saying that I had been preapproved for a credit card upgrade on 19 March 2015. I logged in to my internet banking and the option was there to upgrade to a platinum card and a limit increase. I was offered a large limit but decided not to accept such a large amount but a smaller one. THe next day when nothing had happened I sent a query via the website.Eventually on monday I spoke to a gentleman and he put me through to someone who resent the quote which I had to sign and send back. AFter many calls and nearly R200 worth of airtime, I got through to someone on friday who told me that nothing else was required from me. When I spoke to yet another consultant on monday 30/03/2015 I was told that I need to send my proof of income and copy of my ID. Another quote was sent but only to upgrade the card and not a limit increase. Today the reason was that the income amount I provided was more than what was on the system. Why does FNB give offers if they dont intend to honour them. I have been in contact with Natasha Adolph, who has been very helpful but I am not satisfied with the answer.