If it is a school locker go to the office they have the combination. If it is lock you bought look on the bottom or side sometimes there is a reset button. If there isn't look at the brand and see if...
Your only solution - is to go through every possible combination from 0000 to 9999 until you find the correct number !
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You can try plugging it into iTunes. If that doesn't work, you may have to restore it.
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