Block PPP/IPCP packets after being connected

Hello everyone. I have some questions about the 'PPP' protocol and PPP Daemon in OpenWrt.
While I using the 'PPPOE' for connecting to ISP, OpenWrt uses 'pppd' for obtain the IP from ISP, and ISP send this information to me using 'IPCP' packets over ppp.

But my scenario:
The ISP allow users to be connected just at allowed hours. for example: users just can be connected between 12:00 PM to 5:00 PM, and after that they'll disconnected, or if they trying to connect in prohibited hours e.g 7:00 PM, the request of connection simply refused.
But what if the user just simply block the "IPCP packets" or "PPP Protocol" after being connected(authorized) in allowed times, and then ISP can't disconnect the network using IPCP when the allowed times end. It's some kind of force keeping alive the connection. is that possible?

Leaving the contractual/legal matter aside for a bit, it is unlikely that blocking these packets will result in your desired outcome unless your ISP is either incompetent or very naive and trusting the good-will of it's customers. IMHO, the ISP will simply stop it's end of the PPP link hard, the packets you see most likely are only send out of courtesy so your end of the link can shut down the connection gracefully.

Back to the legal matter, have a look at the contract you agreed on. If you dislike the contract or some of it's clauses, talk to your ISP and see whether you can get them changed. Unilaterally trying to side-step the measures your ISP uses to assert contract compliance can get you into legal hot water quickly, so just don't do it.