You need a csv with the simcard data and osmo-config-merge needs to be in your
path.

To create hlr.db and change the mcc/mnc run:
./provision_hlr.py --mcc 901 --mnc 23 source.csv

This will create the hlr.db and a simcards.csv where the first digits of the
IMSI will be changed to match the MCC/MNC. In order to reprogram the IMSIs of
the SIM cards run pySim-prog:

./pySim-prog.py -p 0 -t sysmoUSIM-SJS1 --source=csv --read-csv=simcards.csv --read-iccid

This is only needed if the mcc/mnc options are used.