Vodacom greed

I have been with cell c for more than 17 years, decided to switch to Vodacom because cell c reception is very bad in the area where I now live. All calls that came in on my Vodacom number show as unknown even those saved in my contacts. I phoned Vodacom and was told I now have to pay R10pm to be able to see the numbers calling. Never have I ever been invoiced to see who is calling me. Why do you charge for a service other networks provides for free.