CELL C Collections System hopeless

I recieved a request from Cell C if they can debit on 18 December and needed to reply thinking that they confirmed our Pay date for December i rep**** yes as per their request.Later the same day i relised that our paydate will not be on that 18th i called their call centre to request that the the date be moved back to the original date and i was advised by the call centre agent that she will submit the request.This is not the first time that i've had such a problem with them and now i'm sitting with another R115 unpaid debit order on cheque account.How can such a big company not be able to change debit order strike dates?Surely the system that they are using should be able to change the strike or someone should be able to manually remove the debit order from the file that they are going to submit to the bank.