Rain wants full payment but provides limited cover

I have a month to month wifi contract with Rain. I did not have cover for the first week of December and made full payment on 9 December. Since I paid for a full month I should receive cover for a full month. Now they are asking for payment of R479.00 again! I understand cover runs from month to month however if I paid full then why am I now not being asked to pay a prorated amount? This means I am paying for services not received. Call centre consultants dont even understand the query and just wastes my airtime.