Lewis daily calls offering credit.

My mom was once a customer of Lewis stores lenasia she finished paying them off early last year .but they keep calling asking her to come take credit that she doesn't need she refuses time and time again but yet the keep calling everything. I asked them to take her off the Client list but the lady say they can't do that. Is it allowed for a credit providers to keep calling and offering you credit even after you told them you don't want to buy ?.