Refund adjusted against earlier pending demand.

My client submitted rectification for AY 2017-18 against demand.
For AY 2018-19, my clients refund got adjusted against demand of AY 2017-18.

Now my client demand for AY 2017-18 got converted into refund and he got refund for AY 2017-18.

Now, how to claim back refund of AY 2018-19, 2 high was adjusted against AY 2017-18.