Most electronic devices (including cellphones) come with a manufacturer's warranty. It may be as short as a month or as long as a year or more. The warranty begins on the day you buy the phone, so determining whether it is still under its original warranty requires you to know this date and the duration of the warranty itself.
Locate the original warranty information card that came with your phone. It will have been packaged in the original box with the phone, the battery and the user's manual.The card will specify how long your warranty was valid.
Find out the exact day that you bought your phone. If you cannot find the original receipt, call the customer service number for your cellular provider and ask for the date the phone was activated. Phones need to be activated at the time of purchase, and the company will keep a record of this date.
Determine whether the current date falls within your original warranty. For example, if you bought your phone on October 1 with a 30-day warranty and it is now December, your phone is no longer in its warranty period.