Bad service from Discovery Health payment department

We have a very bad service from Discovery as alway; and it is a pain to communicate with them. Our request for them to pay for the doctors' services is always moved from one consultant to the next. Their last response is saying now saying our email address is not registered (and they have responded to the same before). I am not sure if this is their latest trick to avoid payment and it is really too much to be taking time to be explaining the same thing to different consultants. We pay them monthly and they get no issues from our side but when it comes to payments they try by all means to reduce the payments so that they can profit more as they aim for us to pay the bills. I think they every work together with companies appointed to collect bills for the doctors as from both side they frustrate us and keep sending the emails saying Discovery Health is not willing to pay. We really need an alternative