Cell C service Poor

Last year I upgrade my Cell C contract, upgrade to a Samsung 5. My phone was blacklisted wrongly by Cell c.<br> I had to go to a Police office to get a affidavit to unblacklist my phone. Send the form through to Cell C. it was unblacklist, since then my troubles start. One month the phone work then its off line again. Phone Cell C, blacklist again. They said the problem sorted. For more than 5 months I'm struggling to get my phone to work.<br> I even went to Cell C store, they phone in now help. Promise they will phone me back. I have to carry my tablet around now with my original sim card just so that I can phone.Phoned Headoffice a week ago, log a call still no help. This goes on for more than 5 months. I have a whole diary full of names and reference numbers, Still my Samsung S5 says if I try to phone. Not registered on network. Correspondence with Cell C, nothing help.But every month my Cell C debit order goes off, but I have no use off my phone. Please help me.