This is how SMS works
Most bulk SMS senders wouldn't use SS#7 as that's the internal phone network protocol suite (or was, last time I looked some years ago). But this company did. That suggests that either they're being treated as a telco by their peers, or perhaps they aren't doing anything, a real telephone company is doing the work for them.
In the GSM network any call or text causes a location lookup from the HLR. This is perfectly normal and not in any way sinister.
How else can the call/text be routed to wherever the phone happens to be today?
Biting the hand that feeds IT
