Stop calling me

I made a payment on 26 March 2015 on my personal loan as agreed with Nedbank.But 31 march 2015 i received a call from Nedbank asking why my account is still not paid.I asked the consultant to give me an email adress so that i can send the proof of payment as she kept telling me and insisting that no payment was made.She said she does not have an email adress she can only give me a fax number well i cant access fax.04 April 2015 i phoned nedbank personal loans explaining the situation and asking if my payment reflects.Wayne said yes and i asked why i was receiving calls He said i need to check with collections department as he is in customer services.Your departments need to communicate you cannot expect me as a clients to clarify all information on your behalf.