A lot of department stores now sell phones. Whether you bought it from a box store or online website, you may need help if it suddenly stops working. All websites are required to provide information about return policies and warranty periods, so they're usually a good place to start.
Here's a few tips if you need to get your phone fixed:
Return policies
Most places have a return policy for phones. Make sure you keep your email or physical receipt and it should say what their policy is.
Warranty period
Some department stores also provide warranty periods. These are typically longer than the return policy and cover most hardware defects that could happen. A lot of these warranty periods are tied with the phone manufacturer and will recommend you reach out directly to them if you need help.
Outside warranty
There's a few options after your phone's warranty has expired. You can still work with the phone manufacturer to get your phone fixed, but since the warranty has expired, you'll have to pay for their services.
Another option is to take it to the many phone repair shops that have opened in the last few years. They're local and you won't have to ship your phone to the manufacturer. Just web search "phone repair near me" and you'll see what your options are.