Useless service

We have a problem with the number ********** . Apparently this number was ported to another service provider which we know nothing of as we did not request for this. If we ask Telkom who this new service provider is they dont know who it is. I am being sent from one department to the other and no one can answer me. How do you not know who you ported the number to. We only pay Telkom every month so we are not aware of a new service provider. Someone needs to sort this out now as it shows this number does not exist and we are loosing clients due to the fact that they cannot get hold of us on this number.