Typically the telco will only set the CNAM data (aka Caller ID name) to some variation of the account holder. CSCO, Cisco, Cisco Systems, Cisco TAC, or something similar. They typically won't let you set it to another company's name. If they do, pick a different DID that you never plan on using for anything else and have them change it (updating CNAM information is extremely inconsistent; you may never get it to show your company name again reliably).

If they won't update the name, you have two options:

1) Have the vendor install a few POTS lines or a fractional PRI and route their calls differently.

2) Set the ANI (caller ID number) for their calls to whatever their real main office number is (I.E. set the external number mask to 800GOCISCO). The CNAM lookup will be performed against their number and show their name. Again, this will only work if the telco allows your PRIs to specify an ANI that you don't own. This kind of depends on how much they like you it seems. :)

PS- CNAM data resides in a database at your telco. The SS7 data stream contains the calling number (ANI) and the destination switch is supposed to query the CNAM server at your telco for the CID name if the called party switch supports CID name.

This idea comes off the tracks when certain telcos (cable and VoIP operators are especially guilty of this) make copies of CNAM databases instead of performing the CNAM lookup properly at the time of the call. If this happens, the CID name will be correct for some people you call but wrong for others. Your only route will be to somehow convince these other carriers to refresh their cache. Good luck with that if it happens.