I have to pay for Medihelp's ambulance clause I never knew of

My wife called an ambulance for my son through our armed response at home. Later on, I find that I have to pay half the ambulance bill because we had to use ER24 and not Netcare 911.

Medihelp tells me that it is stipulated in the contract i signed with them- but I joined them through an online Hippo search and a subsequent telephonic contract, and I don't know of any part where we spoke about ambulances. Now Netcare 911 attorneys are on my back because I can't pay for this ambulance .

As far as i know i was covered for the hospital we went to and therefore that included getting there. I need Medihelp to prove to me that i was informed of this preferred ambulance clause in that call, otherwise they must just pay Netcare 911.