BILLING ERROR

I am ok with the connectivity but i have a problem with billing. I made a promise to pay and paid R100 cause my payments were delayed, so as i was about to make that payment it said the balance is R524. Then after making payment it said i owe R900. I called them and spoke to Jay who didn't want to disclose his surname, i don't know why. He said that there was a mistake and has forwarded to the billing to be investigated and i should expect a call the following day. Unfortunately, till today i haven't received any call. No one has responded to my emails. I don't know what kind of a company is this, that doesn't have proper channels, there are no details for complaints, you just have to call one number and which won't be a success if you call directly from your linked phone cause you will be listening to a machine. Companies don't work like that. Stop ****ming people, already your reviews are bad but instead of making changes, you continue. Solve this matter, dont direct me to your DM or email cause you don't respond there. Btw i've paid again R450 and moved the promise to pay date so that i can give you enough time to resolve the matter. I WON'T PAY FOR NONSENSE, I DONT KNOW WHERE THAT EXTRA R300 IS COMING FROM.