Poor service from Vodacom

I'm having issues with my Vodacom number and its not so long ago since I opened this contract but everytime a person calls me it says private number dont understand why. When u call and tell them they tell me to add extra money to turn it around but how I fail to understand. When a person buys a phone and comes with Sim the Sim card shouldn't give problems. They also give me airtime and no data I fail to understand how so.