Upgrade suddenly declined

Dear Vodacom,

I have been a customer of yours for decades, with no arrears or account problems at all. So I was shocked when I was refused an upgrade today because of my credit score. Although I realise that it does reflect negatively on my profile, I would like to know what has changed. My credit score was the same when I upgraded 3 years ago and this was not an issue at all. What has changed? Does it make any difference that I have been a loyal and paying customer for many years and my history with you is positive? Are you ok with loosing all your clients who do not have good credit scores, because you won't allow them to upgrade? This does not make good business sense to me at all. Regards, TS