I’ve set our modem to band 20-only.
I want to use auto-attach (at+cops=0) but it did not find a network
However, manual attach (with selecting Vodafone’s network) did work
Doing something else for about 30 minutes around the time @Kolja-Vornholt left the reply about searching the network.
Trying the search only gave me seemingly non-related info (“90104”),
But trying the auto-COPS suddenly did the trick and attached in no time.
Carrier Aggregation, i.e. the linking of spectrum bands (Carriers) to a new virtual frequency band is a means to to offer high data rates for LTE-Advanced. However, NB-IoT is specifically designed for use cases with very low data rates and volumes, so there is no requirement for high bandwidth.