As above. The organisation to whom you (allegedly) owe money is Smart Parking, not DRP or CST. Smart have engaged them to chase you on their behalf, but it is still Smart who are the alleged creditor.
If they do take it to court, they'll probably get a law firm to do it for them, but again, they'd be doing it on Smart's behalf, and Smart would still be the claimant, in much the same way that if you had a lawyer representing you (not usually done for parking cases, as they'll charge more than the claim is worth!), you'd still be the defendant, not the lawyer.