Ah, you wrote "at the POS", and since you mention svc adapter and interface, I guess you are using RES 3700.
As far as I remember, there is no built-in way to search for customers with the old svc adapter.
You can find the SVC adapter documentation here
Link
These are the available inquiries, no search, though...
1: ISSUE CARD .............................................................................................................................. 46
2: ACTIVATE CARD ....................................................................................................................... 46
3: RELOAD CARD .......................................................................................................................... 46
4: CASH OUT ................................................................................................................................. 46
5: BALANCE INQUIRY .................................................................................................................... 47
6: BALANCE TRANSFER ................................................................................................................. 47
7: ISSUE POINTS ............................................................................................................................ 47
8: REDEEM POINTS ........................................................................................................................ 48
9: POINTS INQUIRY ........................................................................................................................ 48
10: REDEEM .................................................................................................................................. 48
11: REDEEM AUTHORIZE ............................................................................................................... 49
12: ACCEPT COUPON ..................................................................................................................... 50
13: ISSUE BATCH ........................................................................................................................... 50
14: ACTIVATE BATCH ................................................................................................................... 50
15: MANUAL REDEMPTION ............................................................................................................ 50
16: OFFLINE REDEMPTION ............................................................................................................. 51
18: VOID CASH OUT ...................................................................................................................... 51
75: CANCEL ORDER....................................................................................................................... 51
76: VOID CLOSED CHECK .............................................................................................................. 52