aaah, finally, I thought so too that it's probably very recent for us not to find anything on this number (977).
I just found a missed call from this number as well. It seems to be a service from Djezzy (likely but not sure) for verifying their subscribers who have identified themselves via SMS and not by national ID.
Orascom is suspected (with evidence to back it up) by our government (Algerian) of fraud, tax evasion, espionage, and a whole lot of trouble, so I think this verification is necessary to ensure their network is no longer used by terrorists.
I don't trust these kinds of numbers; I've already received a lot of spam calls from scammers with the complicity of that damn Djezzy.
I’m waiting for an official announcement regarding this procedure; in the meantime, I don't answer calls from unknown numbers ;).