Wrong number, keep ons sending me sms and calls

Hi, a certain miss S Mahantswa, or something like that has got an Foschini/Fashion express/one of your groups accounts and gave my number wrongfully as hers. I keep on getting calls the whole month long, smss that i have to pay my account, statement are beings sms to me and not het because it is the wrong number. I have asked atleast 10x time to the call centre agent to remove my number and add hers on what ever way possibly, when she is in store again or something. But remove my number and they say yes but i keep on getting called and have blocked your numbers but they get to me using new numbers on some way. Please remove my number it is a big hassle