RAF undertaking

My husband was involved in an accident on the 1/12/2014 where G4S money intransit vehicle ploughed into the back of our vehicle he was stationed waiting to turn into the service station to get petrol to come and fetch me at work he had been recovering from back and neck surgery he was due to go back to work in the January that never happened my husband ended up back in hospital due to server back and neck pain up until now nothing has been done they say that the case has been finalized and that the injuries sustained were not serious we still have not been sorted out my husband has been in pain we were sent a RAF undertaking to use to see the doctors with on enquiring but the hospital's and doctors don't accept them reason being is that the RAF don't pay so what must we do now we don't have any money to pay upfront we feel very much so let down