Pathetic accounts system

First of all they get the email address wrong,and no matter how many times I give the correct email address they still don't correct it,even though I don't know how they got the email address.Their consultants tell each a different story when it comes to payments when a upgrade has been done,give different times as to when the admin fee is due.I paid it the same month as the upgrade,they then credit the amount,and not even the whole amount.Where the other money went to i don't know as nobody can explain it to me.They didn't think that the BIS of the blackberry should be canceled due to the upgrade being done and a new device has been issued ,which made me pay more than what I was told originally.When I asked what will be the amount to be paid in June, they told me to call on the 1 June 2015 then the invoices will be issued. Needless to say I called today which is the 1 June 2015 and was told to call back on the 03 June 2015 as it will only be available then.Once again I provided my new address and email address to update,wonder if was done this time.Their service is Worse I ever received and will not recommend them to anyone.How can invoices be issued late,yet payment is expected