Payments

I am a visa credit card customer with id no ********** 509089 ref no: ********** ********** 25/7 I phoned them on 8march 2018 trying to find out my outstanding balance they successfully tell me the amount to pay I then paid on the same day for the purpose of closing the account when I phoned them the following day to find out whether they received the money I paid they told me to wait for few days after some days they phoned me demanding money I owed I told them that I paid the balance emailed the proof of payment on March 8 and they emailed an acknowledgement about the proof of payment they promised me to look for it but to my surprise I've receiving calls daily requesting me to pay the due amount. I don't know what to do now can you help me in this regard. I phoned them using this number: ********** 018