Shocking, pathetic, non existing service

Its now close on 3 weeks and still Cell C can't sort out my problem.my phone shows an error message \Not registered on network"<br> I did not trust the Cell C brand and therefore in April first purchased a prepaid sim card before committing to them.<br> It has now all gone pear shape and David the manger and his regional manager refuse to talk to me.I cant phone their call centre"