Hello,
Thank you for you question.
Currently no Teltonika Telematics Fleet management tracker has functionality to get only GSM based location.
FMB920 and other Teltonika Telematics trackers have AGPS system, which uses mobile-network radio bearers such as GSM, CDMA, WCDMA, LTE to help faster "Warm-up" the GNSS receiver and obtain position Fix faster.
Regards,
Mantas