SA Post Office
Paid for Post Box, but do not have access to it

I have paid my post box before the due date and for the year. Went to post box but was locked. Went into Post OFfice, they said it was locked due to non payment. Next day I returend with proof of payment, but still do not have access, because there was nobody to open the box, the time I went there was 13:44, they have already left for the day! So how many times do I have to go there before I have access to my post after paying for the access to it? My payment receit number 8608761, paid a month before the due date for the year!