This is rather strange.
Why would they single out Susans?
That doesn't make sense
This isn't tagged as an adult site, google would confirm that.
They would have to go out of their way to find and block this site, OR their adult "block" filter contains some very vague word criteria.
Susan's does have a "sexuality" section, and those posts do contain search-able content such as "orgasm" "vagina" "clitoris" "stimulation" "breasts" and other such words that in bulk, might trigger a block filter.
What seems odd, is that as a user, you should have a way to override the filter if you choose.
You might look into that. Your network should not be filtering the internet. That is the job of the software on your phone, and should be user-adjustable.
If it's not, I would switch services as that is ridiculous. A paying adult should be able to do what they want with their phone.