Not Syncing all Channels from my TV provider

I have Premium Xfinity channels with HBO, Starz and lot of channels and iam not able to see those channels in the list

This is normal. Premium channels are not available via TV Everywhere

do we get this option in future to sync premium channels?

No. See What channels are available?

ok, thanks for clarifying. and also is there a way to sync my xfinity movies?

no. Channels is for Live TV....not VOD access.
u would need to use the Xfinty Stream app to access Xfninty VOD and movies etc. or the premium channels app specifically. (HBO,Showtime...etc)