MTN gave my number to somebody else.

My number is given to somebody else without informing me. When I gone into the store the lady told me to call the person and told him that he got my number. That I will not do. This problem is caused by MTN. I had this number for years. FIX this now MTN. I am very upset with this as there is thousands complaints of this. They receive all my text messages and calls now. This is a breach of privacy.