Vodacom contract

I am really disappointed with my experience with Vodacom. I have been with this service provider since I started owning a mobile phone in school. I have had 3 upgrades with the company and now that I am finally due for an upgrade I am told I can't because my credit score is too low.

I don't understand how I was allowed to upgrade 2 years ago when my credit score was lower than it is now. I managed to call the call centre who told me I do not qualify to upgrade yet my vodacom app says I am eligible to upgrade. I have never dishonored a payment to vodacom and have always had my contracts through them.

I would like someone to please explain how I could upgrade previously with a lower credit score than now.