Terrible and shocking service - actually non-existent service

Absolute terrible Service Provider. I did an online upgrade on my wife's contract 3 weeks ago. The upgrade was successful and was advised that my phone would be delivered in 2-3 days. It's been 3 weeks and still no delivery. Every time I do a follow up, I'm advised that it's on its way. Being fed up, I went to a Cell C store to do the upgrade there, but was then informed that they can't do the upgrade as it's still pending on their system. I have phoned the Call Centre to cancel this upgrade which they told me would take 24-48 hours. It's now been a week since then and still the upgrade has not been cancelled. Since then I have called the Call Centre 5 times, spending a total of 6 hours on the phone, only to be pushed from one department to another and nobody can help - all they say is that it's still pending. Being fed up, I them demanded for my contract to be cancelled (it's over the initial 24 months), only to be told once again that I can't even cancel the contract because the system has a "pending query". Seriously, what is one to do to get things done. So now I still don't have my new phone, can't upgrade at a store and can't even cancel the contract? I have since sent the customer care an email giving them notice to cancel the contract and will not be held liable for any further costs on this contract after the 30 day's notice - AND YES I WILL SEEK LEGAL ADVICE IF THEY CONTINUE TO BILL ME.