Billing Errors

If I could give them Zero stars I would. I was overcharged on my August and Sept bill for a data SIM I have. I called numerous times and they advised they aware of the issue as a number of clients was affected and a credit will be passed. I was advised a query will be logged and escalated. Still no credit has been passed and it has been 2 months gone by already. When you ask to speak to a manager , the agent will advise they will request a call back and no one calls you back. I'm still waiting for my credit.