Airtel
Sim number hacking

I AM USING AIRTEL SIM CARD FROM LAST 4 YEARS APPROX... MY SIM NO IS 9867643182, SIM IS REGISTERED ON MY NAME_SUNIL SURYAKANT ACHAREKAR, BUT ONE OF MY FRIEND RECEIVED SO MANY MISCALLS FROM SAME NUMBER WHEN SHE WAS TRAVELLING WITH ME AND MY CELL WAS IN MY HAND..WHEN SHE MAKE CALL ON MY NUMBER SOMEONE RECEIVING HER CALL AND SAYING THIS IS MY NUMBER 9867643182... BUT WHEN I TRIED CALL ON THAT NUMBER REPLY IS SWITCHD OFF or busy.now i am confused if someone hacked my cell number or just a fake... please help me