NuSys Technologies - Employer didn't give me April payment (salary)

Nusys Technologies hired me as a part-time remote software consultant (worked as a software developer) with monthly payment ***** in April and I started working there part-time. I give a minimum of * hours every day for his work and I gave them update on a daily basis. They told me to pay between ** to ** May but now they are not responding to me. Even I have all records of my work there (chats, call records and emails). My last call was done with the CEO on *th May when he said to me that payment will be done between ** to ** May. I have that call recording too. But now he is not receiving my calls nor he is replying back on chat.