[WAF] Update faq.mdx (cloudflare#25258)

Add note for ISP-level blocking restrictions (SPM-2856).

---------

Co-authored-by: Pedro Sousa <680496+pedrosousa@users.noreply.github.com>

Author: zeinjaber

src/content/docs/waf/troubleshooting/faq.mdx

@@ -52,6 +52,10 @@ If you are the site owner:
 - Monitor blocked requests in your Cloudflare dashboard.
 - Allowlist trusted IPs or fine-tune WAF/bot rules to reduce false positives.
 
+:::note
+ISP-level blocks are distinct from Cloudflare or site-owner security restrictions. For details, refer to [Potential ISP blocking](/support/troubleshooting/general-troubleshooting/potential-isp-blocking/).
+:::
+
 ## Bots
 
 ### How does the WAF handle traffic from known bots?