Walmart Family Mobile Making Charges on Previously Canceled service Stafford Texas

Everyone should be aware of how porting over a number(s) from one servie provider works. Having the telephone number in questin, account number, and pin, or passwords, the lines in question are thus canceled and then activated on the new service provider. This being the case, why would Walmart Family Mobile continue to charge a  monthy service fee on accounts that even their representatives agree are no longer active since the date of the port over and can clearly state that to me with the specific dates. And then to continue saying there are no other charges and in disdain tell me to contact finincial institution first, when the charges were disputed. This greedy world has gotten to the root of a once fine and reputable store (Walmart). I guess i will have to wait and see if i am still to be charged next month too.