Hi there.

Admit Card for NEET is considered valid when the Candidate's photo and signature are clearly visible in it. If your admit card does not have your signature you might not be allowed to sit for the examination without a valid admit card. 

Make sure to call the authorities or contanct them by any other means. Only they would be able to hel in this scenario. 

There will surely be problems if you end up in the examination centre without the signature on your admit card. Contact the authorities as soon as possible and rectify this.

All the best!