I have the same problem, ATT DSL, drops internet connection . ATT says my address doesn't have updated service available or any interest in fixing it. Good-by ATT asap. I figured out that the router can't handle multiple devices very well. If I want to print something I need to close the browser, then send the file to print. If we have company and 3-4 people are using wifi, chances are good the router will lock up. This is a recent problem, worked fine for a decade.
Looking at NextLink fixed wireless since ATT doesn't care to keep a customer.
Jim