Well, that's the problem with this business. The data is not yours (belongs to the exchange), the internet is not yours (Airtel etc.). You are simply passing the orders back and forth, and yet you face ire for the downtime. Get used to the client outrage. Your response during these situation will be moot as you grow.
A brief explanation of the user outrage :
"Knowing why it pains does not cure the pain"
Hopefully you will also come up with a policy regarding any profit/loss to the users during the outages.