On the occasion of a party's first appearance through counsel, the attorney whose signature first appears on the initial pleadings for any party shall be the attorney in charge, unless another attorney is specifically designated therein. Thereafter, until such designation is changed by written notice to the court and all other parties in accordance with Rule 21a, said attorney in charge shall be responsible for the suit as to such party. All communications from the court or other counsel with respect to a suit shall be sent to the attorney in charge.