Cannot adhere to a clients request

I settled my account and confirmed that I am no longer interested in their services. According to me, my account has been closed - seeing that I paid the outstanding in full. I keep on getting calls from the store to confirm that I have Rx credit available. I received a call this morning, called the store and spoke to the manger. I requested her to make a note that I do not want to be contacted as I am not interested in their services. Low and behold I receive a sms just now confirming I have Rx garuanteed credit and shoudl visit their store. What do they not understand? I dont want to buy from them. Remove my details!!!!