Seems the CCFC implementation on Telit firmware is not v.250 compliant:
ofonod[445]: Aux: > AT+CCFC=0,2\r
ofonod[445]: Aux: < \r\n\r\n+CCFC:0,7\r\n\r\nOK\r\n
In certain cases the #QSS notification is never sent, or sent too early.
Make sure that we enable #QSS notification only after the modem has been
set as powered. Also make sure that we explicitly query #QSS in case we
missed the earlier #QSS notification.