YOU SAID:

My grandmother ate my hand which was grasping a phone

INTO JAPANESE

私の祖母は電話を握っていた私の手を食べました

BACK INTO ENGLISH

My grandmother ate my hand holding the phone

INTO JAPANESE

祖母が電話を握って手を食べた

BACK INTO ENGLISH

Grandmother grabbed the phone and ate her hand

INTO JAPANESE

祖母は電話をつかんで手を食べた

BACK INTO ENGLISH

Grandmother grabbed the phone and ate her hand