Is it not a quality issue if the mobile phone battery swells?

Foshan 12315 said that it is unreasonable for the business not to change the battery for consumers on the grounds that the battery swells but can still be used. In the recent months, a battery used by Miss Chen under normal conditions began to swell after three or four months. During the warranty period of the battery, Miss Chen returned the battery to the seller for replacement. The seller refused to replace it on the grounds that it could "still be used". "It has deformed, and they still say there is no quality problem with the battery." Miss Chen found this incomprehensible. Different parties have different opinions on whether the swelling of the battery counts as a quality issue.