You said that you needed surgery, not that you already had it. I'm English, but I'm sure you guys have insurance. If it was an injury obtained whilst serving, they are obliged to give you care and treatment, if you were offered a way of free surgery, but chose to go with a Civy surgeon that's your choice to take the debt that was caused by that choice. In summary, you're entitled to care and treatment after receiving an injury during service. I respect you for your service.