Bgv process for PwC

Can some one explain the bgv process of PwC. I got offer from PwC but u know I have absconded from my first company that got 1 week overlap with my 2nd and current company I worked here for 3.8 yrs now

How should i handle this as I dont have any letter frm the 1st company, I do have my friends experience letter but do they call my first company and ask for dates or how should i deal this i should speak to PwC hr few days before joining?