Business purpose, Am From India. I need to obtain a One week VISA Chengdu,Sichuan

for advanced Data Recovery training. I have received an invitation from Chinese Company and I went to nearby Chinese embassy consulate to apply for an entry permit.
First they told me You will get VOA at airport. Now they are telling that two letters are required for entry permit process 1 is Invitation letter form company & 2nd is entry permit issue request.
Can anyone please suggest me on getting a 1 week entry permit for an official training at Chengdu, Sichuan?????