no leeways for payment

I initially signed up for a 20mbps service at R750 - it went up to R845. I continued paying this service, because my gmail was full and couldn't access my invoices, so I did not notice the installment went to R945 , please note the R100 less each month added up, now to R700 , I am now being disconnected??? I asked the accounts person to make an arrangement for me to pay half and half , but this isn't good enough, I am very upset at the services I am paying R850 a month for years now, and I asked for leniency to pay half the arrears end of May and the other half End June, I am being denied, and being told my service is gonna be disconnected, I am trying here, please be understanding, I am even going to downgrade now as I am on a 100mbps package and will be able to afford the lower packages, so please don't treat me this way as I am still staying with your services?