Upgrade declined due to debt review

Been with Vodacom for years, first as pay as you go client and then by contract For the past 3/4 years now we are under debt review, and at first when I'm (or anyone under our contract in our family) is due for an upgrade, there was no problems. Until now recently... I was due for upgrade in January... Went to Vodacom to upgrade...and was declined. We never miss a payment and we make sure we pay the debt review on time. We know what we can afford. Why did Vodacom only now decide to not let me upgrade??? But previous years and while under debt review they allowed it?? We are a big family under the same contract and new cellphones is very costly!! That is why we chose contract so we can keep up!! I am so disappointed in the way they suddenly declined my upgrade and will for sure end the contract with them as soon as we are legible to do so.