Cell C
Bad Coverage Durban North

I have been having issues with 3G in over a month in the Durban North area. It goes on edge and very slow..
I called the call centre, they told me to go to Options, Device, Advanced Settings, and register which will reset the BB . This has not helped.
I am due for an upgrade this month, and have been happy with Cellc for years. But recently it has got very bad - my house and the tower have not moved - so please advise what the problem is and is it going to get fixed. Otherwise I will have to choice but to switch providers...