ISPs are starting to use this tactic more and more - when they discover torrenting sites, they don't block them on your IP - instead, they stop resolving them in DNS (which, presumably, blocks them for all!)
As noted, one easy solution is to use alternate DNS solutions.
I, personally, use the CloudFlare DNS services at IP addresses 1.1.1.1 & 1.0.0.1. CloudFlare is a major Internet provider - just not in the "last mile" delivery of services. Their DNS servers are non-logging and if you want REAL protection, they offer DNS services over encrypted channels!
Of course, if you use a VPN, the DNS servers you use will usually be those assigned by your VPN provider - which can ALSO be overridden to use the CloudFlare (or other) DNS services!