Telkom says my number no longer exists

After numerous complaints to our local Telkom office and trying various setting changes I am just not coming right. I have been with telkom for years and last year upgraded and got a new phone. People now struggle to get hold of me as the phone keeps telling them that my number no longer exists. I am running a professional business and my phone is my livelihood. Telkom keep brushing me off telling me it is my problem. What do I do. I am at my wits end.