Paid Up Credit card been handover 3 times in one year

<p>my wife credit card has been paid since 2016/01/08 and we recieve a proof of paid up letter however since then for the past year this same account has been handover to the 3 different debt collector,this is not happing and again this monring my wife receieve another sms from another debt colloer demanding payment before the list her on credit burea</p>