@Rauha: There is no such thing as standard GSM frequencies. All kind of regions use different ones, and European is nowhere a "standard".

See:
https://en.wikipedia.org/wiki/GSM_frequency_bands
https://en.wikipedia.org/wiki/UMTS_frequency_bands
https://en.wikipedia.org/wiki/E-UTRA

Only recent modems address this insanity properly by supporting literally all possible bands. Unfortunately Jolla didn't use one of those in their first device, because they come only in the latest SoCs.