Over billing and no response

Good morning. We bought a LTE from Telkom for our company. We have been billed 3 times for the LTE in one month, with extra added on. I have queried this with them on 26 October, followed up on 5 November and still no one has bothered getting back to me. i get the same response from them: it has been logged. This morning I once again send a mail, but this time I added that If i do not get a response I will get it resolved via Hello Peter. I quickly got a response saying: It will be investigated. 3 Weeks of investigating and still this has not been resolved.