Bad Customer Service by so called Service Champions

I was a MTN customer and switched to Vodacom. My contacts has been calling me recently asking if i had called them on my previous number. I found it strange as i have not had this number for a very long time. Today 3 of my family members all called me asking me the same thing. I decided to call MTN and ask why this is happening and they told me that my number has been recycled. I then asked the so called service champion why they have access to my contacts and she was arguing with me and telling me it is impossible that could happen without even trying to find out why this is happening. So flippen rude person i spoke to NO customer service experience whatsoever. She then dropped the call on me as I was trying to explain to her that i understand what she's saying but the person is harassing my contacts. How is this even possible. Thee worst Service provider ever and what am i suppose to do now with this person having all my data on their sim.. So irritated. They should NOT be calling themselves Service Champions