First, if the parties have signed an entrustment contract with the lawyer of first instance, and the termination is not mentioned after the second instance, then they need to re-entrust and pay the fee.
Second, it is not stipulated that a lawyer must be hired in litigation, so whether to hire a lawyer or not, the parties can continue to be represented by a lawyer of first instance according to their own language, or they can be replaced or represented by others.