The distress call is used if you become stranded without fuel. When you call for a distress ship, your ship will be refueled, and your bank account will be charged for the fuel usage. The cost for fuel is 1 credit per 1 unit of fuel. This is an expensive way to fuel your ship! You should probably try to top off your tanks whenever you have the chance on the ground...
NOTE: We recommend you always keep some money in the bank to cover the cost of an emergency refueling.