Reliably Detecting Mobile ISP Identification for Web Tools?

Our 'What is My ISP?' tool struggles with accurate ISP identification for mobile clients, often misattributing IPs from carrier networks or VPNs to generic cloud providers. For example, a typical lookup might yield:

dig +short myip.opendns.com @resolver1.opendns.com
192.0.2.1

dig +short 192.0.2.1.sbl.spamhaus.org
; <<>> DiG 9.10.6 <<>> 192.0.2.1.sbl.spamhaus.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 62232
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

# Problem: Often returns generic data, not specific mobile carrier.

We're looking for robust server-side techniques or API endpoints to achieve more precise mobile ISP identification. Anyone faced this before?