Paid Up Letter

The worst service provider. I had a contract with cellc which has been paid up and a proof of payment sent. Earlier this month I received a statement and to my surprise I now owe them R 1 796. Several follow ups have been made regarding a paid up letter and till this day, I haven't received any communication. A case was opened and this is the reference I was given (***) saying I'll be contacted within 2 working days. It's almost a month now with no assistance and everytime I phone them I'm told the matter is being escalated. Is this how we *********** people?