You can get the 2015 download by contacting customer service. You paid for 2013 they will send 2015 for the charge you have already paid.
To contact TurboTax customer service/support use their contact website during business hours.
Submit your question/problem during business hours and then use the option for Call (a phone number will be provided for Call) to speak directly with a TurboTax agent -
Note: The Call option will not be available when TurboTax Support is closed.