I had my phone for 2yrs and I cracked my screen days after having it I did not get the phone replaced because the phone still worked now it's starting to malfunction trying to get an replacement phone but I lost my imei number that came with the phone, with an ZTE zmax there is not an back to take off and see this number and I screwed on getting an replacement
If the screen is still working/legible, try dialing *#06#. This will display your IMEI #.
Otherwise, try calling customer care, as they should have your IMEI # on file.
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