Vodacom's credit vetting system

I have an account with Vodacom and pay them every month never skipped a payment. Today i went and wanted to take a contract and I am told the dropped my credit score?Why on earth would they do that? I pay my accounts on time they should I just wish I can take my business else where this is ridiculous. I have a contract with them for the past year, they should be give me a good customer service. The guy at the store asked me if i have ever skipped a payment? i told him look at the history, not once have i skipped.