account said not paid but its paid

this is really irritating now an honestly i dont even know what to say..account holdee paid her account on 1/5/2015 the next thing on the 04/05/2015..she gets a call from the call center to say she didnt pay her account..fine POP was send to the store n the store said they faxed to the head office n on the 12/05/2015 to say she did not pay n need to take the POP to the store again......fisrtly these waste of transport money n my mom is frustrated now n confused....so can u all stop harrasing my mom n do your job....why is the head office not calling the store to get their POP ?....this is not acceptable n they even have a nerve to ask her to the back to the store with the POP.....i am going to take this sdtupid POP to the store.....i pray n hope my mom wont get another stupid from call fron u