Someone else in SA has exactly the same cell number as me

Someone else in SA has exactly the same cell number as me, sometimes my friends try to call me, without any luck they get through to anouther lady with the same number as myself? i dont know if she is able to receive any of my banking details and who knows what else personal info of me... and then on the other hand i do receive strange phone calls of people speaking Tswana/sepedi/zulu, ( i dont know the language )

How should I go about sorting this out and getting her sim stopped???