is this for real? if it is then i f to be careful . But the tac thing,its not easy to get it if ur not the person. coz u cant do it online i thnk or prolly im wrong..i thought u f to use an atm machine to do it, evn to change ur mobile phone number. Just say if tht person changed the mobile num, they must f did it thru a atm machine (cant change that thru online system)
so, only some1 who has ur atm card can do tht for sure

probably, coz unless u revealed ur details, or gave ur atm card to some1 ,its not easy for an outsider to do so..unless of coz, pb staff itself is involved or ppl close to u