[alexkinch]

See my answer here - https://news.ycombinator.com/item?id=9300690 - about why you're getting O2 for a Giffgaff number (Giffgaff is an O2 MVNO, and owned by O2's parent Telefonica as it happens).

Re: a Twilio UK landline number coming up as JT, as you're probably looking at the results of a SS7-MAP command that returns the SMS routing info for a particular number, in this case it's likely that JT look after the SMS side of that number (routing for voice and SMS and the networks themselves are generally quite separate).

[EvanDotPro]

Ah, glad someone else with experience is in this thread. You've saved me a bunch of typing.