There is a cap for rider and certain companies do cover ambulance fees. As for claiming as per charged, it will be the main plan that is deducted from your Medisave. Usually I will advise my client if possible try to get the rider together with the main plan, as you won't have to worry any small amount not claimable.

As for matchy: if the consultant talk very fast,do feedback to them or ask them anything you are not sure. Coz I do ask my client whether they und what I'm explaining as sometimes I do und that insurance can be confusing for them

Hope it helps ! =)