Nedbank issuing letter of demand even though an arrangement was made

<p>I have made an arrangement on my credit card earlier March/ April 2017 for payment in the amiunt of R500.00 per month on/before the 30th of each month. I have recently received a sms confirming that n letter of demand was posted and that i should collect same. I am upset due to the fact that arrangement was made and that i have kept my arrangement with them. I cannot pay more that the amount of R500.00. </p>