I couldn't fly to the USA due to ill health, advised Delta Airlines and they offered me a credit. I can't use the credit and my insurance company won't pay out on my claim because I've been offered a credit. I have been on their website looking for flights to the USA but the only way I can use the credit is to spend another £900 on top of what I already paid. Despite long emails and telephone calls I am no further forward. When is a credit from Delta not a credit - when it can't be used.