How to stop erase of data after clicking erase option mistakenly in android device manager
Unfortunately, if you issued the command to erase the phone, there is no taking it back.

If the device you sent the erase command to does not have service, it would not receive the command; but then you would not be able to track the disconnected device either.

Once it gets an internet connection, and receives the command to erase, it will start. 

If you happen to find the device prior to it receiving the command to erase, you may be able to remove Android Device Manager to prevent loss of data.