There are a couple of ways cid can be delivered on co lines.
Check with the voip provider what method they are using.
I have seen incompatibity with cid it was with ds816 (aka dcs24) and certain exchanges, never with os7000 and voip.

There is a mmc I the 400's where you can change the cid type from memory.

Otherwise upgrade to 5.03 and go straight voip if you can