Number deleted after using for 15 years

I have been a loyal customer for over 15 years. I left the country for 3 months and upon returning I was informed my sim card/number was deleted. I was not told before hand at all. This number is very important to me for various security checks, municipal account links etc. It has not been assigned yet but I have been told there is nothing that can be done which I suspect is nonsense. At the Menlyn branch I could not be helped either and agents over the phone are useless. I will be joining another network because this is honestly unjust. They have not rep**** to my emails and I want to escalate this matter.