Our website is hosted on wordpress and now we are facing an issue of files permissions its getting changed automatically by particular time duration in daily basis.
At initially file permission is (755 or 644) but after few time ago it change itself and becomes files permission to 000.
The actual issue is files could not execute over my website its showing fatal error because of permission of file is not permitted to execute it.
due to this problem i was unable read/write/update any file of my website
even tho i was unable to change it via FTP/Wordpress/Cpanel of any of this
what should i do now
please reply

Certainly sounds like your WordPress host needs to be asked why they are doing this.