The worst customer service I have ever received

$ times I have requested a call back to change my billing date stretching back since the 15th of July. Each time I get a response stating that one of your agents will be in touch with me shortly. to this date I have yet to receive a single call and I am unable to change the date on the app./

Working from home and remotely I need access to the internet in able to work and now that you have susp[ended my service I am unable to work

Even after I called in I still have not received a call back. I have used up all my airtime to try and sort this out to no availa.