Cannot rate service because there is none

I wish to cancel one of my numbers *** that are on a month to month since my contract ended, I keep on getting transferred then the call cuts, I am wasting my time with MTN as I always battle to get Invoices, billing getting service from MTN is a no no, I cannot rate the service because there is none. I cannot believe that they are so *********** that the staff cannot even solve a simple problem.