Is this a PCN for entering a road prohibited to motor vehicles?
If so then no, you can't normally submit representations against a PCN that isn't addressed to you as you have no legal involvement as a third party.
The correct course of action is for the hire firm to submit representations that they are a hire firm and then name you as the hirer. At which point, assuming all the paperwork is in order, the council can cancel the initial PCN and serve one on you instead.
How did you receive the initial PCN if it wasn't sent to you? Did the hire firm make you aware?