Paid Up but listed as BAD Payer

<p>My Cell acounts are up to date and i am due for an upgrade but do to NDS listing me as a bad payer i cannot upgrade my contract.</p> <p>When i try contacting their call centre no on is available to take my call.</p> <p>I want proof of what account is not paid up from them because from what Cell C tells me and what I know from my debits that go off I am paid up.</p>