I hate to hear about your tank. And the treatment from customer service. We do expect more from major distributors that we are giving or money to.
Ive called them before about ordering a custom tank and they told me I would have to get with a local store because they only deal in wholesale and do not deal with the public.
Usually how it works with wholesalers is that if there is a problem you return the merchandise to the store you purchased it from. One reason is because the retailers mark up the prices. So things can get very problematic if they sell to a store, and have to refund an individual. The retailer probably marked it up 50%. So if a refund was needed, they would be refunding lets say $500 for a tank they sold for $250.
Plus they may get better prices on shipping to a store rather than an individual. Or they may be able to put several tanks together and ship them so the shipping cost is offset.
It sounds like to me they are trying to get you to find a local store to go through , possibly for these or other reasons. Unfortunately for you , the retailer you bought the tank from no longer deals with DSA, and it sounds like for some reason they are refusing to either refund your money, give you the new tank, or order a new one for you.
The retailer shouldn't be telling you , we'll help you if DSA will help us. It puts all the burden on you to have to go around them and to deal with DSA, which DSA will not do and is not their policy to do. That could be the reason DSA is not dealing with them anymore.
I hate to hear you are having these kind of problems. But as was stated earlier, you will probably have to get this resolved from the store where you purchased the tank. Even if it means going with a different brand tank.