Refusing hospital claims

My son was admited to hospital on two occasions on 23-09-2015 and then again on 29-09-2015. On 29-09-2015 bllod test where done by Mauff AC & Partners and Momentum refusing to pay as wrong tarrif code was used(according to them) whre when I speek to Mauff AC & Partners they are saying that right tarrif code was used and momentum wants them to use different tarrif code.<br> On23-09-2015 blood tests where done by Dr Du Buisson which momentum refuse to pay out as it is double claim where Dr Du Buisson dissagree and holds me liable for payment. <br> In both cases I seen on my statement that Iam not liable for payments untill I got phone calls from Mauff AC & Partners and Dr Du Buisson telling me that I am liable for these payments.<br> Why do I have an expensive plan that covers up to 200% if Momentum refuse in hospital claims in full and then when I do contact them about this issue advise me to go and fight it out myself as it is not their isssue but mine. Once I get that authorisation for hospital admision I do expect all hospital claims to paid up to 200% and not to be chased around for payments.